Home Welcome Getting Started Conferences Authors

1994 Part 1     Front Cover (1994 - Part 1)    No author information available Summary: Not available         Table of Contents (1994 - Part 1)    No author information available Summary: Not available         Conference Information (1994)    No author information available Summary: The following topics were dealt with: MRI; accelerator magnets; stability, quench, and protection; very high field magnets; power conditioning and components for SMES; large conductors; SMES design; fusion magnets; motors, generators, and MHD; HTS coils; VAMAS; CICC stability; Maglev; magnetic bearings; AC losses; HTS current leads; detector magnets; transformers and power transmission; current limiters; BSCCO tapes and wires; YBCO films; Nb-Ti and Chevrel phase materials; HTS film microstructure; J/sub c/ and magnetization in HTS; flux dynamics and pinning; HTS bulk materials; TBCCO and HBCCO; melt processing; large area films; AIS materials; multilayer films; microwave losses; surface resistance; flux structures; thick films; HTS microwave circuits; HTS junctions; LTS SQUIDS; mixers; A-D converters; RF passive devices; magnetometers; proximity effects; bolometers and IR detectors; digital circuits; HTS SQUIDS; nanobridges; microwave resonators; digital modelling and CMOS hybrids; detectors; arrays; LTS junctions; SFQ shift registers; field effect devices; oscillators and voltage standards; SFQ arithmetic and logic; X-ray detectors; flux flow devices.         ITER-a world class challenge and opportunity    C.C. Baker, B. Montgomery and K.L. Wilson Summary: The International Thermonuclear Experimental Reactor is an activity by the US, Japan, the Russian Federation and the European Atomic Energy, to design a fusion engineering test reactor based on the tokamak concept. The main objective of ITER is to demonstrate the scientific and technological feasibility of fusion energy. A six year engineering design activity began is 1992. The paper provides a design overview and describes key components including the superconducting magnets and in-vessel. The ITER International Organization and the US Home Team Organization is described.         Space applications and implications of high temperature superconductivity    G.W. Mitschang Summary: The High Temperature Superconductivity Space Experiment (HTSSE) opened new opportunities and applications for high temperature superconductivity. Space missions inherently benefit from reduced weight, size and power and HTS offers an order of magnitude improvement in these as well as simultaneously improving performance. The paper provides a short history of HTSSE and the current status of the next phase. The author outlines lessons learned from building the first space experiment and some challenges still remaining. He addresses the unique problems faced when HTS is "qualified" for use in the space environment and concludes with projections and predictions of what is next. The paper is intended to be of general interest and addresses material and electronics aspects of space applications. Summary results of tests conducted at the Naval Research Lab and elsewhere are presented as they relate to space qualification of HTS.         SQUID magnetometers for biomagnetism and nondestructive testing: important questions and initial answers    J.P. Wikswo Jr. Summary: For two decades, academic and industrial researchers worldwide have used SQUID magnetometers to measure magnetic signals from the heart, brain, lungs, liver, nerves, skeletal muscle, stomach, intestines, eyes, and other organs, and have invested heavily in developing and promoting this technology. While there are as yet few accepted clinical applications of SQUIDs, various trends are encouraging. The introduction of SQUIDs to the nondestructive testing (NDT) of aircraft and other structural systems and materials is following a similar course: most of the effort is directed towards instrumentation development and demonstrations in simple systems, and instruments suitable for specific commercial applications are just now being prototyped. To assess the potential of either technology, it is useful to ask critical questions: why are we doing this, what have we learned so far, how easy is it, what does it cost, how might we best utilize advances in digital SQUIDs and high-temperature superconductivity, and what can competing technologies provide? Answers to such questions can help identify those specific technological niches for which SQUIDs are uniquely suited, and guide the optimization of SQUID systems that are targeted for particular NDT or biomagnetic measurements.         High-field magnets and high-field superconductors    S. Foner Summary: This paper gives a brief historical review of the development of high magnetic fields and high field superconductors including brief summaries of the early developments of high magnetic fields and the Francis Bitter National Magnet Laboratory (FBNML). The start of the first revolution (when large critical currents in Nb/sub 3/Sn were observed in high magnetic fields) and the development of practical superconductors are outlined in parallel with selected applications developed at Lincoln Laboratory, FBNML, and other departments at MIT. Many large scale superconductor applications, supported by governments, are reviewed briefly; although many models and preliminary designs were completed, a number of US initiatives for large superconducting systems were discontinued. This summary of high-field superconducting applications is followed by an outline of the development of the highest field superconducting materials, comments on the false reports of high T/sub c/ superconductors which appeared throughout the 1970s, and the start of the second revolution (when the high T/sub c/ oxides were reported).         Recent progress in high-T/sub c/ superconductivity: what would make a difference?    M.R. Beasley Summary: Recent progress in the fundamental understanding of the high-temperature superconductors is reviewed with an eye toward its practical implications. An attempt is also made to identify a research agenda for the future, needed in support of the applications of these new materials.         Trials and triumphs of superconductivity: the making of Oxford Instruments    M. Wood Summary: In 1959 the author and his wife founded The Oxford Instrument Company to design, manufacture and supply equipment for generating high magnetic fields to a small scientific research community. Fundamental discoveries in the field of superconductivity soon introduced radical changes to the technological base and put the company on the road to rapid expansion in a number of different markets. Growth from a small private company into a diversified, science-based, international operation employing nearly 1500 people and with sales of over $170 million, has presented them with many interesting technical, business and human challenges. The author describes some of the landmarks along the way, and highlights elements from his experience which may be of interest to others embarking down the same track.         A cryogen-free open superconducting magnet for interventional MRI applications    E.T. Laskaris, R. Ackermann, B. Dorri, D. Gross, K. Herd and C. Minas Summary: A 0.5 T cryogen-free superconducting magnet with an open geometry has been designed for use in MRI-guided minimally invasive surgery and other interventional procedures. The magnet consists of a split pair of coils to allow surgeons direct access to the patient within the field-of-view of the imaging system. The magnet is wound using Nb/sub 3/Sn tape conductor and is maintained at approximately 10 K using a pair of Gifford-McMahon refrigerators. High-Tc superconducting current leads have been used in order to minimize the heat leak to the magnet. A passive quench protection system was developed for this unique magnet geometry. High quality MR images have been produced and used for interventional procedures. Descriptions of the design, fabrication, and test results of the magnet are presented.         A 6 T refrigerator-cooled NbTi superconducting magnet with 180 mm room temperature bore    M. Urata, T. Kuriyama, T. Yazawa, K. Koyanagi, K. Yamamoto, S. Nomura, Y. Yamada, H. Nakagome, S. Murase, H. Maeda and O. Horigami Summary: A 6 T NbTi superconducting magnet, cooled by a 4 K GM (Gifford-McMahon) refrigerator has been developed. Magnetic material, Er/sub 3/Ni, is used as the regenerator to cool the coil to liquid helium temperature. The central field strength in the 180 mm room temperature bore is designed to be 6 T. NbTi coil dimensions are, 215 mm in inner diameter, 279 mm in outer diameter, and 240 mm in axial length. The coil winding is an epoxy-impregnated structure without a bore tube, thereby reducing mechanical disturbances. The coil heat is removed through the outer metal cylinder. A pair of Bi(2212) current leads has been developed to reduce heat leakage into the 4 K level. A cold diode is used to protect the coil even if the oxide lead is burned out. The magnet attained 6.45 T central field at 3.61 K coil-winding temperature.         Structural design and analysis of a cryogen-free open superconducting magnet for interventional MRI applications    C. Minas and E.T. Laskaris Summary: The structural design and analysis of a cryogen-free open superconducting magnet for interventional MRI applications is presented. The magnet assembly consisted of two identical halves connected together by four posts. The magnet separation allows a surgeon access to the patient within the field-of-view of the imaging system. Each half of the assembly consisted of three superconducting coils, a stainless steel bobbin, a copper thermal ring, and three overwrap rings. The suspension components of the magnet consisted of eight radial straps and eight axial rods. A structural analysis was carried out that considered the differential thermal contraction caused by the cooldown to the magnet cryogenic operating temperature, and the electromagnetic forces on the coils when the magnet is energized at the design current value. The results are compared to the equivalent stresses caused by a simulation of a quench that was initiated at the inner diameter of one of the superconducting coils. The post-quench thermal transient analysis predicted a nonuniform 3-D temperature field in the range of 10 to 178 K and asymmetric electromagnetic forces on the superconducting coils. The three dimensional structural model of the assembly was developed in ANSYS.         Persistent superconducting switch for cryogen-free MR magnets    B. Dorri and E.T. Laskaris Summary: A persistent superconducting switch which allows a cryogen-free MR magnet to be ramped up to its designed magnetic field and parked in a persistent state has been designed, built, and installed in a magnet. The switch uses niobium-tin tape superconductor which is laminated with stainless steel foil for structural rigidity. Due to its high electrical resistance, the switch is well suited for high inductance magnets. Moreover, the switch is designed such that its ramping heat load into the magnet is minimal and within the capability of the refrigerating cryocoolers which are used to cool the magnet. The compact design of this switch permits a quick conversion between the normal and the superconducting states. In this paper, the design criteria for such a switch and its relationship to the cryogen-free superconducting magnet is discussed. Furthermore, the stability tests performed on a sample switch is presented. Finally, detail design of a switch which has been used in a high inductance, cryogen-free, open MR magnet is discussed along with its electrical and thermal performances.         Cooling structure for 6 T NbTi superconducting magnet directly cooled by cryocooler    T. Yazawa, K. Koyanagi, M. Urata, T. Kuriyama, Y. Ohtani, S. Nomura and H. Maeda Summary: This paper describes the cooling structure for a 6 T NbTi superconducting coil directly cooled by a cryocooler. The cooling structure was designed to remove AC loss of the coil lest the coil temperature should exceed the current sharing temperature during coil charging. A copper cylinder surrounding the outer surface of the coil was adopted as the cooling structure. Indium sheet was inserted between the copper cylinder and the coil to improve thermal conductance. Stainless steel wire was wound on the copper cylinder so that the radial stress at the boundary between the copper cylinder and the coil was kept compressive. Temperature difference between the coil inner surface and the copper cylinder was lower than 0.1 K while charging the coil.         A dual refrigerator assembly for cryogen-free superconducting magnet applications    K.G. Herd, E.T. Laskaris and P.S. Thompson Summary: Reliable refrigeration is critical to the viability of cryogen-free superconducting magnets. The servicing of a refrigerator coldhead must not interrupt the magnet operation. A dual refrigerator coldhead assembly is described in this paper which enables the disconnection of a coldhead for servicing while a second coldhead provides continuous cooling. The two-stage Balzers UCH-130 coldheads are thermally connected to the cryostat thermal shield at the first stage and to the superconducting magnet at the second stage. The assembly includes high-T/sub c/ superconducting current leads heat stationed between the first and second stages of the coldheads in order to minimize the heat leak to the magnet. Vibration isolation components minimize the transmission of the coldhead vibration to the magnet and the thermal shield. This paper describes the design, fabrication, and testing of the dual refrigerator assembly.         Status of LHC programme and magnet development    R. Perin Summary: The Large Hadron Collider (LHC) is a superconducting accelerator/collider for protons, heavy ions and electron-proton collisions in the multi-TeV energy range, which will be installed at CERN in the 27 km tunnel of LEP. This new facility will mainly consist of a double ring of high field superconducting magnets operating in superfluid helium at a temperature of 1.9 K. To reach the wanted beam energy (7 TeV for protons) the main dipole magnets will operate at about 8.4 T and the quadrupoles at 220 T/m field gradient. These main magnets have a two-in-one configuration with the magnetic channels for the two beams placed in a common yoke and cryostat. The LHC will have more than 10000 superconducting magnetic units. The arcs of the machine will require about 1250, 14 m long dipoles and 400, 3 m long quadrupoles. After a general outline of the project with more detailed information on the design of the magnets, the paper describes the state of magnet R&D and presents results of short models, among which one reached the record dipole field of 10.5 T, as well as of industry made full scale prototypes which have been successfully tested and measured.         The SSC full cell prototype string test    P. Kraushaar, W. Burgett, L. Cromer, J. Gannon, D. Haenni, M. Hentges, T. Jaffery, M. Levin, A.D. McInturff, G. Mulholland, D. Revell, D. Richter, W. Robinson, D. Voy, J. Weisend II and J. Zatopek Summary: At the conclusion of the SSC (Superconducting Super Collider) half cell magnet string testing program in February, 1993, the preliminary data analysis revealed that several substantive technical questions remained unresolved. These questions were: (1) could the high voltages to ground (>2 kV) measured during fault (quench) conditions be substantially reduced, (2) could the number of magnetic elements that became resistive (quenched) be controlled, and (3) did the cryostats of the magnetic elements provide adequate insulation and isolation to meet designed refrigeration loads. To address these and other existing questions, a prototypical full cell of collider magnets (ten dipoles and two quadrupoles) was assembled and tested. At the conclusion of this testing there were definitive answers to most of the questions with numerical substantiation, the notable exception being the heat leak question. These answers and other results and issues are presented in this paper.         Cryogenic tests of the first two LHC quadrupole prototypes    P. Genevey, J. Deregel, J. Perot, J.M. Rifflet, P. Vedrine, J. Cortella, A. Le Coroller, F. Rodriguez-Mateos, N. Siegel, T. Tortschanoff and A.P. Verweij Summary: Two LHC (Large Hadron Collider) twin aperture quadrupole superconducting magnet prototypes were constructed at CEA Saclay, in the framework of a collaboration agreement between CERN and CEA in Saclay. Their main characteristics are: 3.05 m length, 56 mm coil aperture, 180 mm between the two apertures, 252 T/m nominal gradient at 15060 A. They have been tested and measured in the 1.8 K Saclay test facility in a horizontal cryostat. The magnets are instrumented in order to investigate their behaviour during cool-down, stand-by, powering and current ramping, quenching and warming-up. The paper presents a summary of the cryogenic, mechanical, pressure and electrical measurements. The 15060 A nominal current was reached with little training. The quench protection heaters are efficient down to 3000 A. Losses during ramping up and down are reported.         Magnetic measurement test results of B&W 1 m quadrupole magnets    C.M. Rey Summary: This report summarizes the magnetic measurement test results on the QSH series of collider quadrupole superconducting magnets. There were four quadrupole magnets built in the QSH series. These magnets had a 40 mm aperture and were approximately 1.2 m in length. Test results showed that the measured transfer function was within 0.3% of the design value at operating current and temperature and remained linear to within 0.3% from 656 A to 6714 A. In addition, all multipoles were well within the CQM system specification with the exception of b5. The origin of the large b5 term and the anomalous current dependence of the transfer function are briefly discussed.         Ramp-rate limitation test of cable-in-conduit conductors with supercritical helium    S. Jeong, M. Takayasu, J.V. Minervini and J.H. Schultz Summary: It has been found on the United States Demonstration Poloidal Coil (US-DPC) and in 27 strand subsized cables of pool boiling cable-in-conduit conductor (CICC), that there is critical current degradation due to fast ramping of the magnetic field. The characteristics of this ramp-rate limitation phenomenon are investigated by using a 27 strand Nb/sub 3/Sn cable in supercritical helium at 6 atm. A 3 m long cable-in-conduit conductor is prepared noninductively and tested in a background field up to 9.5 tesla with maximum ramp rate of 1.6 tesla/second. The ramp-rate limitation results are compared with results of the ramp rate test of the US-DPC and previous experiments. The experimental data are analyzed to identify and understand possible sources of ramp-rate limitation.         The effect on stability and thermal hydraulic quenchback of perforating the jacket of a cable-in-conduit conductor    L. Dresner Summary: This paper continues earlier work on the reduction of the quench pressure in a double-jacketed cable-in-conduit conductor achieved by perforating the inner jacket. The present study examines the effect of the perforations on the stability margin and on the onset of thermal hydraulic quenchback.         Stability analysis of multi-strand superconducting cables    N. Amemiya and O. Tsukamoto Summary: When a normal zone is produced in one or a few strands in a multi-strand superconducting cable by a localized disturbance, the current in the normal-transited strand transfers to the others via contact resistance between strands. Heat generated in the normal zone also diffuses to the other strands. The stability of the multi-strand superconducting cable against local disturbances is much influenced by these current transfer and thermal diffusion. The influence of the copper resistivity on current transfer and stability is studied. When we plot the MQE on "contact resistivity"-"contact thermal conductivity"-plane, there are a stable region with large MQE and an unstable region with small MQE. The small contact resistance and small contact thermal conductivity between strands are preferable from the view point of stability. If the contact thermal conductivity is small, the transition from the stable region to the unstable region is drastic.         Quench energy and fatigue degradation properties of Cu- and Al/Cu-stabilized Nb-Ti epoxy-impregnated superconductor coils    S.L. Bray, J.W. Ekin, D.J. Waltman and M.J. Superczynski Summary: In comparative measurements of small-scale epoxy-impregnated Cu-stabilized and Al/Cu-stabilized Nb-Ti test coils at 4 K and 5 T, the heat energy required to quench the Al/Cu-stabilized coil was 4 to 12 times greater than for the Cu-stabilized coil, depending on the relative operating current. Also, the coils' stabilizer resistivity (/spl rho/) was measured as a function of mechanical fatigue to test for strain-induced degradation. The /spl rho/ of the Cu-stabilized coil is relatively unaffected by fatigue, while that of the Al/Cu-stabilized coil increases with fatigue. However, in these coils, having a typical stabilizer:superconductor ratio of 4:1, the degradation of the Al/Cu-stabilized coil begins to saturate after several hundred fatigue cycles; after 2000 fatigue cycles to 0.2% strain, the /spl rho/ of the Al/Cu-stabilized coil is still 2.6 times lower than the /spl rho/ of the Cu-stabilized coil. Furthermore, after annealing the Al/Cu-stabilized coil at room temperature for 48 hours, the /spl rho/ degradation was reduced by 76%. Thus, the use of Al/Cu stabilizer may offer substantial improvements in magnet stability, even where the magnet is subjected to fatigue degradation from repeatedly energizing the magnet.         Quench protection of very large superconducting magnets    A.V. Dudarev, V.E. Keilin, Yu.D. Kuroedov, A.A. Konjukhov and V.S. Vysotsky Summary: The feasibility of utilization of cold switches for quench protection of very large superconducting magnets (e.g., for SMES) is considered. The scheme of quench protection of large SMES is suggested. The necessary number of sections can be easily evaluated. Destructive superconducting switches seem to be the best solution. The switch has to be properly designed to avoid arcing and to offer a possibility to change the destructive elements in a reasonable time without warming up large portions of the winding. A suggestion is also made to make use of the temperature dependence of the electrical resistance of the dump resistor. A proper choice of its mass can result in 25 percent decrease of a quench load.         Stability measurements on a 1-T high temperature superconducting magnet    J.W. Lue, L. Dresner, S.W. Schwenterly, D. Aized, J.M. Campbell and R.E. Schwall Summary: A high temperature superconducting magnet based on Bi-2223 conductor was built at the American Superconductor Corporation. The magnet was constructed by a react and wind technique using conductors made from a metallic precursor process. It has a winding ID of 25.4 mm, OD of 87.6 mm, and height of 107.3 mm. A heater, two thermometers, and several voltage taps were built into the high field region of the magnet for stability measurements. The magnet generates 1.1 T central field at 4.2 K when operating at 1 /spl mu/V/cm over the entire conductor length, including all the joints. Stability measurements were performed in background fields up to 2.5 T from 4.2 K to 77 K. Stability margins more than 2 orders of magnitude higher than a low temperature superconductor were observed.         Development and test of a BSCCO-2223 HTS high field insert magnet for NMR    D.W. Hazelton, J.A. Rice, Y.S. Hascicek, H.W. Weijers and S.W. Van Sciver Summary: In this paper we describe the successful design, fabrication and test of a model high field insert magnet utilizing BSCCO-2223 tape conductors. This insert magnet is the first phase of a program to demonstrate the use of HTS conductors for the generation of the high magnetic fields required for NMR. The magnet, designed and fabricated at Intermagnetics, consists of five double pancake coil modules stacked in series to give overall dimensions of 48 mm outer diameter, 72 mm length and a 19 mm clear bore. The double pancake coil modules were prepared using a wind and react technique followed by encapsulation with low temperature resistant epoxy. The assembled magnet was then tested at both 77 K and 4.2 K in fields of up to 17 Tesla. The high field tests were conducted at the NHMFL. At 4.2 K, with a 17 Tesla applied field, an additional central field of 0.24 Tesla was developed before transition to the normal state. These results indicate the ability of these materials to be used in high field insert coils.         Study of Nb/sub 3/Sn superconducting joints for very high magnetic field NMR spectrometers    P. McIntyre, Yu Wu, Gan Liang and C.R. Meitzler Summary: A new, simple method for making Nb/sub 3/Sn-Nb/sub 3/Sn superconducting joints is described in this paper. Joints with resistance 5/spl times/10/sup -13/ /spl Omega/, which is good enough for NMR spectrometers, have been fabricated, using a simple and reproductive procedure. An in situ joint test system and joint test results are presented.         Some considerations on the design and construction of a 12 Tesla magnet for testing high-Tc superconductors    L. Garcia-Tabares, J. Aleixandre, J. Calero, F. Moyano, M.J. Saenz de Buruaga and R. Iturbe Summary: This paper describes the design and construction of a 12 T Nb/sub 3/Sn-NbTi magnet for testing high-Tc superconductors. The magnet is a first prototype of a future and bigger test station and it has been made to validate the main concepts as well as the manufacturing techniques. The first part describes the magnetic and mechanical design of the magnet with special attention to the computation of magnetic couplings, mechanical stresses and quench calculations, while the second part analyzes the construction of the magnet and the first results.         Large current and low voltage switching devices using HTS thin film    T. Ikegami, K. Shingai, Y. Yamagata and K. Ebihara Summary: A high temperature superconducting (HTS) thin film has a potential to control large currents using its transition between a superconducting state and a normal conducting state. In this paper an equivalent circuit model of a HTS thin film is presented to design a power conditioning circuit as an inverter which can handle large currents at voltages less than 1 V. Device model parameters of a HTS thin film were determined by comparing quenching characteristics calculated by a circuit simulation program (PSpice) with those measured experimentally. A temporal behavior of resistance of the HTS thin film quenched by a self-current which was simulated using the model were compared with experimental results. An inverter circuit using the HTS thin film switched thermally is designed and the characteristic of a switching operation with a photovoltaic cell is also shown.         Power control by superconducting magnetic energy storage for load change compensation and power system stabilization in interconnected power system    M. Tada, Y. Mitani and K. Tsuji Summary: This paper describes a load change compensation by a superconducting magnetic energy storage (SMES) which is assumed to be installed in a power system for power system stabilization. A simultaneous control strategy of SMES for load change compensation as well as for power system stabilization in a longitudinally interconnected power system is derived. Several numerical examples demonstrate the significant effectiveness of the SMES.         Comparative study and simulation of optimal converter topologies for SMES systems    I.J. Iglesias, J. Acero and A. Bautista Summary: In this paper a comparative study between different topologies for SMES (Superconducting Magnet Energy Storage) systems is presented. The study is based on the simulation of different options by using EMTP (Electromagnetic Transients Program). The comparison is mainly centered on two converter types: current and voltage converters. Although both topologies could be used for SMES systems, the simulation results give an excellent tool to select the more appropriate topology for any specific application. All the topologies analyzed are based on self-commutating devices (GTO or IGBT) and PWM mode control. This allows a fast and independent adjustment of both active and reactive powers, AC current harmonics minimization and four quadrants (P,Q) operation.         Development of a 50 A-fast response, magnetically controlled persistent current switch    K. Noto, Y. Kono, M. Matsukawa, M. Itagaki, T. Ishida, K. Chiba, T. Tatsuki, H. Homma, N. Sadakata, T. Saito and O. Kohno Summary: We have developed a 50 A-fast response, magnetically controlled persistent current switch (Magnetic PCS), which is thought to be necessary also for a small to medium scale superconducting magnetic energy storage (SMES) system. A 10 m-long, 55 core, in-situ processed CuNb composite wire (0.3 mm /spl phi/, B/sub c2//spl sim/0.6 T, I/sub c//spl sim/136 A at 4.2 K and 0 T) with high resistivity CuNi alloy matrix was noninductively wound on a FRP bobbin and set into a control magnet which can be swept up to the maximum 1.2 T within 2 sec. The magnetic PCS was combined with a small superconducting magnet (0.5 H, 50 A, 5.5 T) and realized a persistent current mode at 50 A. The fast response was checked with a combination of an outer resistance load and by a switching-off of the magnetic PCS in a persistent current mode. The switching-off time of the magnetic PCS was shorter than 0.3 sec. An energy retaining test for about 50 min. was also performed.         Optimal design of the superconducting persistent current switch with respect to the heater currents and the operating currents    T.K. Ko, Y.S. Oh and S.J. Lee Summary: The temperature characteristics of the persistent current switch (PCS) for superconducting magnet systems were analyzed by using the heat transfer equations. The optimal conditions for the design of the PCS were derived in this paper. The maximum operating current in a persistent mode was 100 A (at 1.5 T). The PCS was opened after several tens msec by heater currents. The heater current which could minimize thermal losses was 150 mA. The experimental results of the designed PCS agreed well with the calculated results.         A protection system for small high power SMES with power semiconductors working at cryogenic temperature    J.F. Karner, H.W. Lorenzen, F. Rosenbauer, J. Schaller and R.M. Schottler Summary: A protection system for a superconducting magnetic energy storage (SMES) device is presented. It uses switchable semiconductors at cryogenic temperatures which were examined recently. The protection system will be tested at the SMES pilot plant under construction at Technische Universitat Munchen. Two profoundly studied applications for SMES will be examined experimentally with this testing plant.         Development of a 1 kA, 50 Hz superconducting converter    O.A. Shevchenko, H.H.J. ten Kate, H.J.G. Krooshoop and M.A. Fedorovsky Summary: A single-phase, thermally switched superconducting power converter operating at mains frequency is being developed and tested by the authors. Typical design values of the device are: input voltage of 220 V; input current of 7 A; output voltage of 1 V; and output current of 1 kA. The average output power is about 750 VA, with an efficiency better than 96%. Test results of the full scale power converter while ramping up and down a superconducting magnet and a comparison with the theory are presented. The power converter will be installed as a part of a power supply system controlling the current of a separator magnet located in Ukraine for an iron ore recycling process.         Conductor joint performance during the Ebasco team SMES POPE (Proof of Principle Experiment)    D.W. Scherbarth, O.R. Christianson, E.F. Daly, T. Kupiszewski, D. Marschik, J.M. Pfotenhauer, M.K. Abdelsalam, O.D. Lokken and J.S. Waldrop Summary: A joint in the superconductor and stabilizer is added to the ETM conductor in the POPE. The joint design is similar to that proposed by Westinghouse for the SMES ETM field joints. Fabrication of the joint is described. Measurements on the performance of the superconducting joint operated in subcooled He II and of the stabilizer joint at 14 K are reported. Measured superconductor joint resistance is 1.6 n/spl Omega/, which agrees with previous analytic calculations. The stabilizer joint RR matches the conductor stabilizer RR. The joint met or exceeded all operational requirements throughout the experiment demonstrating its reliability and small joule heating.         High voltage breakdown measurements of a large area SMES-ETM mockup in gaseous helium and air    J.H. Azzola and D.T. Hackworth Summary: Breakdown voltage measurements of a SMES-ETM (superconducting magnet energy storage-engineering test model) mockup are presented for gaseous helium and air at room temperature. The mockup dimensions are 1.35 m long by 0.15 m high. Four critical configurations are simulated (layer-to-layer, dewar-to-layer, coil-to-dewar and turn-to-turn) under four pressure conditions (0.25, 0.5, 0.75 and 1.0 atmospheres). The experimental results for the first three configurations are in rough accord with published data of breakdown voltages in air and helium (Paschen curve). The thin G-10 insulation layer of the fourth configuration provides an excellent insulation capability. Experimental breakdown voltages are compared to worst-case design specifications at one atmosphere. All worst-case safety factors exceed 10. The results indicate that design voltage specifications are adequate for operation in a worst-case quench scenario at one atmosphere helium.         Fast switching characteristics of magnetic persistent current switch for SMES    N. Sadakata, K. Uchiyama, K. Goto, T. Saito, O. Kohno, Y. Kouno, M. Matsukawa, K. Noto, H. Honma and T. Tatsuki Summary: Cu-Ni matrix Cu-Nb multi-core composite wire for a magnetic persistent current switch was developed for SMES. Switching characteristics of small PCS coils up to 300 A were investigated simulating the practical switching operation. Fast current decrease was observed at the critical magnetic field for the transport current, however, turn-on recovery was not reversible after decreasing the field. An original procedure was devised and fast turn-on operation was achieved.         Performance characteristics of the 60 kA SMES conductor    J.M. Pfotenhauer, M.K. Abdelsalam, O.D. Lokken, Z. Jiang, J.S. Waldrop, S. Yang, O.R. Christianson, E.F. Daly, J.E. King, D. Pavlik, E. Brogren, D. DeGraaf, F. Kessler and A. Ludbrook Summary: We report the operating characteristics of the monolithic SMES conductor designed for operation at 60 kA, 5.1 Tesla in a 1.8 K bath of subcooled helium. Details of the experimental arrangement and procedures are presented as background. At 1.85 K the conductor has been operated up to 75 kA, and with maximum field conditions of 4.75 Tesla. Conductor performance is compared to the load line and design point of the Engineering Test Model (ETM). Transient stability is also demonstrated. Maximum conditions experienced by the conductor were limited by facility operation rather than by the conductor itself.         A new approach to measure the electric boundary resistance between high current carrying stabilized SMES conductor and its high strength aluminum supporting structure at 4.2, 77 and 300 K    L.O. El-Marazki Summary: A new approach to measure the electric boundary resistance (EBR) between high purity aluminum (HPAL) stabilized conductor and its high strength aluminum (HSAL) supporting structure in large superconducting magnetic energy storage (SMES) coils is introduced. The magnetic forces on the conductor are supported by the HSAL structure. For better protection of the SMES coil, the conductor and the structure are in electrical and thermal contact. We have designed and conducted an experiment to measure the EBR under equivalent operating conditions. The experiment is conducted under different compressive loads at 4.2, 77, and 300 K. The electric boundary resistance (EBR) /spl rho//sub B/(/spl Omega/-cm/sup 2/)=aL/sup -b/ is a power function of the load L. The constants a and b are functions of temperature. This paper reports on an experimental method of determining the electric boundary resistance at different temperatures and different compressive loads.         Investigation of aluminium stabilized superconductors    P.I. Dolgosheev, G.G. Svalov, V.E. Sytnikov and A.V. Rychagov Summary: Two types of aluminium stabilized superconducting cables: soldered and pressed have been under investigation. The paper describes cables, manufactured from multifilamentary NbTi/Cu wires in high purity aluminium, or copper-clad aluminium with a cross-section of 4/spl times/9 and 4.6/spl times/37 mm/sup 2/. Dependence of contact resistance on the "superconductor-aluminium matrix" interface, on transport current and magnetic field from 0 to 3 T, have been studied. Contact resistance was varied within the range from 1.4/spl times/10/sup -11/ to 2.2/spl times/10/sup -10/ Ohm/spl times/m. Dependence of contact resistance on the cable construction and electrical and physical characteristics of its components was analysed theoretically and experimentally. Discrepancy between experimental results and classic theory predictions is discussed.         European development of high performance Nb/sub 3/Sn strand for the ITER model coils    E. Salpietro, H. Krauth, A. Szulcyk, M. Thoener, C.E. Bruzek, H.G. Ky, R. Garre', S. Rossi, M.V. Ricci, M. Spadoni and J.L. Duchateau Summary: The ITER model coils will use two types of strands, one with high Jc, HP I, one with low hysteretic losses, HP II. Main specifications for the two strands are: HP I: Jc (nonCu)>700 A/mm/sup 2/ at 12 T @ 4.2 K, hysteresis losses<600 mJ/cc (+-3 T); HP II: Jc (non Cu)>550 A/mm/sup 2/ at 12 T @ 4.2 K, hysteresis losses<200 mJ/cc (+-3 T). HP I strand performance is likely to be achieved by internal tin Nb/sub 3/Sn, HP II by a bronze route strand. About 25% of the 26 tonnes required by the model coils will be contributed by the European Community. The companies EM-LMI, Italy (for internal tin) and Vacuumschmelze, Germany (for bronze route) have been selected by ITER for the strand production. The achievement of HP II performance was already demonstrated by Vacuumschmelze on a 10 km strand manufactured for NET in the frame of a former contract. On the other hand, the HP I internal tin strand was to be developed. In view of this, a contract has been assigned to GEC Alsthom Intermagnetics, France, to have a back-up option for internal tin strand. EM-LMI (HP I strand) and Vacuumschmelze (HP II strand) have successfully manufactured Nb/sub 3/Sn multifilamentary wires complying with ITER specifications. Work is in progress at GEC Alsthom Intermagnetics to achieve HP I strand performances.         Industrial development of internal tin Nb/sub 3/Sn strands for high field applications    R. Garre, S. Conti, G. Donati and S. Rossi Summary: Europa Metalli-LMI, in the framework of the NET-ITER project on thermocontrolled nuclear fusion, has developed and optimized the fabrication technology for internal tin multifilamentary Nb/sub 3/Sn strands. The ITER project technical specifications require strands with high critical currents (700 A/mm/sup 2/) associated with low hysteresis losses (<600 mJ/cm/sup 3/-3+3 T). Modifications to the conductor layout were gradually carried out during development of the strands thus maintaining the high critical currents and reducing the losses. Current densities of 850 A/mm/sup 2/ with losses of 550 mJ/cm/sup 3/ were reached. Furthermore, the manufacturing technology developed by Europa Metalli-LMI enables industrial unit lengths greater than 1 kilometre to be obtained. This paper reports activities which have led to the manufacturing of the conductor fulfilling ITER specifications.         Recent progress in Nb/sub 3/Sn development at Oxford Superconducting Technology    R. Hentges, K.R. Marken Jr., Y. Zhang, J. Lichtenwalner and S. Hong Summary: The demand for superconductors that have improved properties at high applied magnetic fields has led to developments in the design and processing of Nb/sub 3/Sn superconducting wire. Oxford Superconducting Technology has been producing Nb/sub 3/Sn products for a number of years and continues to develop Nb/sub 3/Sn wire that will meet the aggressive demands of today's technology. This paper will discuss some recent progress Oxford Superconducting Technology (OST) has made regarding the development of Nb/sub 3/Sn wire for 750 MHz NMR applications. Also discussed will be OST's progress in development of internal Sn conductors for very high field magnets that generate 20 tesla or more.         RRR measurements on a SMES-ETM mockup superconductor    K.T. Hartwig, L.C. McDonald, J.D. Harper and C.Y. Hua Summary: An unconventional, easy to perform method is used to determine the in situ residual resistivity ratio (RRR) of the major stabilizer region of superconductive magnetic energy storage (SMES) engineering test magnet (ETM) 60,000 amp composite superconductor. Measurements are taken by the eddy current decay (ECD) method. A primary benefit of the ECD technique is that measurements are possible at 4.2 K with superconducting filaments present. By taking measurements at 4.2 K and room temperature, the stabilizer RRR can be determined without concern for conductor geometry. Results show that this method holds promise as a tool for monitoring the residual resistivity of heavily stabilized superconductors under normal operating circumstances (wound into a magnet and below T/sub c/).         Feasibility study on separation of several tens nanometer scale particles by magnetic field-flow-fractionation technique using superconducting magnet    O. Tsukamoto, T. Ohizumi, T. Ohara, S. Mori and Y. Wada Summary: The principle of a new magnetic separation using field-flow fractionation is explained and its basic characteristics are studied by numerical simulation. The numerical simulations show that separation of weak paramagnetic particles of several tens of nanometer scales is feasible.         Application of the spinning technique to the production of high beta seamless superconducting resonators for particle accelerators    V. Palmieri, R. Preciso, V.L. Ruzinov, S.Yu. Stark, L. Badan and I.I. Kulik Summary: Superconducting resonators for high beta particle accelerators are multicell structures made of niobium or of niobium-sputtered copper. In both cases the resonator bases are traditionally fabricated by spinning or deep drawing half-cells and electron-beam welding them together at the level of the equator; cells are then welded to one another at the level of the iris. Although after several years of research, this manufacturing procedure has become well-established both for niobium and for copper cavities, full-penetrating electron-beam welds increases production costs, and may easily jeopardize the quality of results in both cases. The authors have developed an original technique for the preparation of seamless 1.5 GHz cavities by simply lathe-spinning a planar disk or a seamless tube. Both niobium and copper can be easily manufactured with high reproducibility and significant savings in manufacture costs.         A split magnet system for quasi-optical gyrotron    M. Parizh, J. Bascunan, G. Ciancetta, W. Mischler and P. Winn Summary: A split superconducting magnet system has been built for use in a 175 GHz quasi-optical gyrotron for generation of high frequency power. The quasi-optical gyrotron, an alternative to the more conventional microwave cavity gyrotron, may have advantages or even be necessary to achieve the performance objectives for future plasma heating applications. The design resolved such important problems as ohmic heating of the cross bore shields, mirror separation, and the magnetic mirror effect. The superconducting magnet consists of four NbTi coils. The cross bore inner diameter is 56 mm. The cavity wall inclination is 10/spl deg/ to the horizontal axis. The main bore diameter is 143 mm. During the first test, the magnet produced a 6.2 T field in the cavity with uniformity better than 1%. The split design accommodates the resonator without interference with the resonator mode and unacceptable ohmic heating. Three current leads allow different currents to be introduced in the winding halves thus tilting the central magnetic field. The magnet has retractable current leads. The vacuum space of the cryostat is good to at least /spl sim/10/sup -8/ Torr and is free of oils and other hydrocarbons.         Electrical and thermal behavior of patterned superconducting disks    L. Bromberg, M. Sidorov, R. Mints and T. Holesinger Summary: Apparatus for the investigation of low and high-T/sub c/ superconducting spirals has been designed and built. The device is capable of measuring the characteristic of superconducting spirals. The superconducting spirals are on a normally conducting substrate. The normally conducting substrate serves as a shunt between the superconducting turns, serving as a distributed quench protection resistor. Samples with both high and low electrical resistance substrates have been tested on this apparatus. Preliminary results of the tests of both high-T/sub c/ (Bi-Sr-Ca-Cu-O) and low-T/sub c/ (Nb-Ti) thick-film spirals have been investigated. Current distribution in films during quench has been studied experimentally. Generation of normal zone and hysteresis current-voltage characteristics have been discovered in high-T/sub c/ superconducting spirals on silver plate. It is shown that frequency of generation of normal zone depends at under certain conditions (transient current, magnetic field, temperature and resistivity of substrate). The results are being analyzed with models.         Investigation of quality of high-resistive coatings of superconducting wires with acoustic emission method    S.A. Nikulin, V.G. Khanzhin, V.I. Goncharov, A.K. Skikov, A.E. Vorobjova and K.A. Mareev Summary: The mechanism and kinetics of fracture of electrolytic chrome coatings on multifilamentary Nb/sub 3/Sn-based superconducting wire have been investigated with the methods of acoustic emission (AE) and electron microscopy when developing superconductors for the ITER magnetic system. Coatings 1, 3, and 8 /spl mu/m thick of the following three types were obtained by varying the electrolyte composition and the mode of precipitation process: milk chrome (Cr); hard Cr; and black Cr. The detected acoustic signal and AE spectra were processed in digital form with a specially designed analyzer of AE signals. Milk Cr coatings are shown to have the greatest crack resistance at any coating thickness, the same is for black Cr, but at thickness of 1 to 3 /spl mu/m. In these coating the microcracks formation is going by the ductile mechanism. Hard Cr coating have the least resistance to brittle cracks at any thickness.         Magnetic shielding of small high power SMES    U. Brammer and H.W. Lorenzen Summary: Small high power SMES in toroidal and solenoidal geometries are compared. The toroidal 1.4 MJ SMES currently under construction at Technische Universitat Munchen serves as example. The hypothetical equivalent solenoid is surrounded by a ferromagnetic shield, so that the stray field of the toroidal SMES is not exceeded. The shape of the shield is optimized with respect to the mass by using a stochastic strategy in combination with a deterministic method. Finally the superconductor losses and the eddy current losses in the shield are calculated for a sinusoidal load cycle.         Micro SMES magnet configurations for reduced stray field applications    M.K. Abdelsalam Summary: Reduced field coil configurations offer an attractive design alternative for small superconductive magnetic energy storage (/spl mu/SMES) systems. These commercially available systems are currently being used for improving the power quality in power conditioning sensitive processes. A reduced field design of /spl mu/SMES would allow its use in high-field sensitive environment. In this paper, proposed multiple parallel solenoids enclosed in one container with alternating field directions is presented and compared to a single solenoid. The parametric study covers stored energy, conductor volume, and overall magnet system dimensions. The efficiency of stray field reduction compared with the conventional single solenoid is also presented.         Design of SMES with reduced stray field    G. Schonwetter and J. Gerhold Summary: A design for an improved 50 kWh SMES arrangement was made concerning the selection of an appropriate conductor, the determination of forces, efficient quench protection and mechanical strength calculation. The improvement relates to a drastic reduction of the magnetic stray field. This goal can be obtained by adding a second or even a third solenoid in such a way that the magnetic moments of all solenoids neutralize each other. Various methods to reduce the stray field were discussed and then the most promising solution-the one which produces the smallest magnetic stray field in combination with acceptable geometrical dimensions and conductor amounts-was analysed for further design. The coil calculation was based on a typical NbTi superconductor in order to match its critical data with the results of the optimized coil configuration.         The advantages of using high-temperature superconductors in high-duty-cycle applications of SMES    S.M. Schoenung, R.L. Bieri and T.C. Bickel Summary: Superconducting magnetic energy storage (SMES) has been proposed for use in applications with high-duty-cycle or discharge/charge cycling rate. Such applications include transit system electric support and frequency stabilization of transmission lines. When cycled frequently, the thermal load to the cooling system is dominated by eddy current or ac losses. In systems with small energy storage capacity, the refrigeration system cost associated with ac losses can dominate the total system cost if the coil uses conventional superconductor and liquid helium cooling. If high temperature superconductors operating at liquid nitrogen temperature could be used then significant savings in refrigeration cost and hence, system cost, are possible. The HTS conductor does require a twisted configuration to realize these savings. Analysis and results for SMES systems ranging in size from 1 MJ/1 MW to 10 MJ/10 MW and operating at up to 1 Hz are presented.         Structure and cost scaling for intermediate size superconducting magnetic energy storage (SMES) systems    M.S. Lubell and J.W. Lue Summary: The Superconducting Magnetic Energy Storage (SMES) Engineering Test Model (ETM) was sized to be extrapolated to a full-scale utility system and only warm structural support was practical. If this constraint is removed, then smaller systems structurally reinforced with cold mass are more cost effective than supported with warm mass. Higher field is also more advantageous and thus the bore of a 20 MWh magnet is an order of magnitude smaller than an ETM. Both aluminum and stainless steel supports were considered and the weight of 1-100 MWh systems were determined. The cost of the SMES magnet scales as 0.5 power of stored energy. The cross over in stored energy where magnets supported by warm structures becomes cheaper was also determined.         Design and cost studies for small scale superconducting magnetic energy storage (SMES) systems    D. Lieurance, F. Kimball, C. Rix and C. Luongo Summary: Design and cost studies were performed for mid-size (1-5 MWh), cold supported SMES systems using alternative configurations. The configurations studied included solenoid magnets, which required onsite assembly of the magnet system, and toroid and racetrack configurations which consisted of factory assembled modules. For each configuration, design concepts and cost information were developed for the major features of the magnet system including the conductor, electrical insulation, and structure, as well as all other systems in the plant. These studies showed that for 1 MWh-class systems, the costs of solenoid and toroid magnet configurations are comparable and that the specific configuration to be used for a given application should be based upon customer requirements such as limiting stray fields or minimizing risks in development or construction.         Protection study of the Babcock and Wilcox SMES coil    Xianrui Huang Summary: Babcock and Wilcox (B&W) is working with Anchorage Municipal Light and Power (ML&P) to design, manufacture and install a 30 MW, 1800 MJ SMES system in Anchorage, Alaska. This will be the first mid-sized SMES system that will demonstrate full four-quadrant utility application. One design option considered for the SMES magnet is an enthalpy margin stabilized coil. A protection code has been established to study the quench performance of the coil. This paper presents the results of this study and compares different protection methods. The paper also discusses the impact of some key design parameters on coil quench performance.         Field analysis for a SMES magnet with radial force balance    J.L. Smith Jr. Summary: The old concept of a radial force balanced coil is examined by calculating the magnetic force distribution from well known exact solutions of the quasi static magnetic field equations. The derived coil geometry is very nearly a torus of a circular cross section. The outside field has the distribution of a single poloidal line current which is a virtual image of a poloidal current sheet on the coil surface that terminates the outside field. The inside field is from a toroidal surface current that terminates the inside field. The J/spl times/B forces are all normal to the current sheets. The magnitudes of the current sheets are adjusted for radial force balance. For a radius ratio of 0.121, the resultant normal force is outward and uniform to about 4%. Thus a simple hoop structure around the minor circumference will support the coil. Vector addition of the two current sheets gives a helical surface current on the surface of the torus.         Statistical estimation of disturbance energy due to conductor motion in rotor windings of superconducting generator    T. Takao, K. Iwasaki and O. Tsukamoto Summary: In a previous work, we have derived a theory to statistically predict the stability characteristics by statistically estimating the size of the conductor motion. In this paper, we apply this theory to predict the stability characteristics of rotor windings of a superconducting generator. Quench tests of the model rotor for the 70 MW superconducting generator were conducted as a part of the activities of super-GM project. The theoretical results are compared with the test results and the agreement of both the results is reasonably good.         Internal stress influence on high current density superconducting magnet performance    M. Arata, T. Hamajima, O. Ohsaki and T. Hirumachi Summary: Dry-wound superconducting solenoids offer good manufacturability of large bore magnets but occasionally suffer from premature quenches triggered by small heat generated within the magnets. The principal source of heat is thought to be conductor motion induced frictional heating and/or filler material fracture released energy in windings. This paper describes major specification, stress analysis and training performance and their relation to a series of magnets that were constructed and tested to establish stabilizing methods of a large bore dry-wound superconducting solenoid. The results suggested that conductor motion took place even though radial stress in the magnet was still compressive and a conductor was expected in its original position.         Temperature dependence of critical current density of AC superconductor and the effect on AC quench current degradation    S. Torii, H. Kasahara and S. Akita Summary: For the development of large-current-capacity AC superconducting cable, it is important to consider the temperature dependence of the critical current density of AC superconductors. To this end, critical current density was evaluated from the magnetization /spl Delta/M, measured by SQUID between 4.5 K and 7.5 K. This value was compared with that obtained by measurement of the same sample using the four-wire method between 4.2 K and 8.0 K, and a good agreement was observed. Therefore, the critical current density evaluated from /spl Delta/M could be considered as a transport critical current density. Also, it was confirmed to be degraded drastically with temperature rise. From simple evaluation, it is considered that the effect of this phenomenon cannot be ignored for AC quench current degradation of large-current-capacity AC superconducting cables, because of AC loss. The cause of this phenomenon is discussed using the pinning force dependence on temperature and magnetic field.         Quench currents of AC superconductor in supercritical helium    P.C. Michael, K. Ryu and O. Tsukamoto Summary: Supercritical helium (SHE) is proposed as a coolant for AC superconducting fault current limiters because it provides better electrical insulation than conventional pool-boiling helium. However, the effect of SHE cooling on the current carrying capacity of AC devices is presently unknown. Quench currents were measured for two single-strand NbTi conductors and a tightly-wound two-layer coil at 0-200 Hz frequency and 0-1 T DC background magnetic induction in boiling atmospheric helium (LHE) and 6-atm, 4.2 K pressurized helium (SHE). The AC quench currents for the Cu30%Ni matrix wire were 20/spl sim/30% lower in SHE, while the Cu10%Ni matrix composite showed almost identical quench currents in both coolants. Analysis suggests that higher temperatures resulting from the Cu30%Ni smaller thermal diffusivity may be responsible for its reduced current capacity in SHE.         Stability of Al-stabilized conductors for LHC detector magnets    F.P. Juster, J.C. Lottin, L. Boldi, R. De Lorenzi, P. Fabbricatore, R. Musenich, D.E. Baynham and P.L. Sampson Summary: The magnets actually under design for the Large Hadron Collider detectors at CERN, ATLAS and CMS, are based on Al stabilized conductors. The windings of these magnets are big structures epoxy impregnated and indirectly cooled by two-phase LHe. Energy releases due to epoxy cracking or to friction between cables could quench the whole magnet. In order to prevent this occurrence, the stability against thermal disturbances must be carefully studied. This paper deals with the development of numerical codes which are able to calculate the recovery or the propagation of a 3D normal zone in a nonhomogeneous and anisotropic medium. Three different numerical codes are described. The codes were tested through the comparison of their prediction with the measurements of the minimum energy required to have a quench propagation on the mock-up of the DELPHI magnet at Rutherford Laboratory.         Transient stability of SMES monolith conductor with normal stabilizer    Y.M. Lvovsky, J.A. Waynert and S.F. Kral Summary: This paper presents an analysis of the transient stability of monolith conductors for a 0.5 MWh, 30 MW SMES system. Two configurations are considered an enthalpy stabilized and a cryostable conductor. The two dimensional transient stability model includes steady-state and transient heat transfer, current diffusion in the stabilizer, current sharing between stabilizer and strands, and thermal resistance between the superconducting cable and the stabilizer. The stability margin is determined for the enthalpy stabilized conductor and the dependence of the conductor stability on conductor parameters is analyzed. For the cryostable conductor, the stability model is used to determine the characteristics of the conductor recovery dynamics.         Stabilities of the Rutherford cables with Cu matrix and CuMn barrier    A. Kimura, S.W. Kim, N. Kimura, Y. Makida, T. Shintomi, H. Hirabayashi, T. Mito, A. Iwamoto and J. Yamamoto Summary: Superconducting coils used for high energy accelerator magnets are usually fixed with epoxy resin in the fabrication processes called "curing". The assembled magnets in the processes have shown different critical current degradation figures due to excitation ramp rate even if they were made in the same manner. The ramp rate dependences of degradation seem to be affected by AC losses between strands of the Rutherford cables (inter-strand AC losses), which are easily affected by the curing conditions. Although they can be reduced by increasing cross-over resistances between strands, the stability problems caused by current sharing between strands may arise. It is important for such kinds of superconducting accelerator magnets to clarify the mechanisms of the AC losses and stabilities of the Rutherford cables. Experimental studies on the AC losses and the current sharing problems for several types of cable samples have been performed.         Stability and quenching in high-temperature superconductors    Y. Iwasa, H. Lim and M.I. Yunus Summary: Two experiments, both on stability and protection issues for high-temperature superconducting (HTS) magnets, are described. Each experiment, with a silver-sheathed BiPbSrCaCuO(2223) tape test sample cooled by a cryocooler, covers the temperature range 20/spl sim/50 K in a zero magnetic field. In this paper, preliminary results on normal zone propagation are presented. Experiment 1 measures normal zone propagation in both longitudinal and transverse directions in a 3-layer test pancake coil; experiment 2 measures temperature distributions, both spatial and temporal, along a length of a conductor undergoing quenching in the longitudinal direction. These results are consistent with those of a simulation code.         Stability models for high-T/sub c/ superconducting conductors    E.E. Burkhardt, S. Nakamae and J. Schwartz Summary: As the properties of high-T/sub c/ superconducting tapes improve, practical design considerations require more detailed analysis. Here, the authors report investigations of the stability of high-T/sub c/ superconducting tapes for magnet applications operating at 4.2 K. As a result of the broad range of temperature during a transition and the strong temperature dependence of the material properties of both the superconductor and the stabilizer, the finite element method (FEM) is used to solve the heat conduction equation. Analytic solutions for particular operating modes are also included.         Manufacture and testing of the superconducting wire and cable for the RHIC dipoles and quadrupoles    A.F. Greene, M.G. Garber, A.K. Ghosh, D. McChesney, A. Morgillo, R. Shah, S. DelRe, G. Epstein, S. Hong, J. Lichtenwalner, P. O'Larey, D. Smathers, M. Boivin and R. Meserve Summary: Production of superconducting wire and cable for the Relativistic Heavy Ion Collider (RHIC) dipoles and quadrupoles is now complete. This report presents the final statistics generated during the manufacture and testing of this cable.         Heat treatment issues for shrinkage alleviation of NbTi cable    M.J. Nilles Summary: Shrinkage of the NbTi conductor during coil curing has been observed to have a significant manufacturing impact. While controlled heat treating of superconductor cable prior to winding can dramatically improve the coil appearance and ease subsequent manufacturing operations, excessive heating can adversely affect conductor performance, e.g. critical current, interstrand resistance, residual resistance ratio and process sensitivity. Aluminum stabilized conductor, where aluminum is applied via conform cladding or co-extrusion, is also impacted by these concerns. Models of potential degradation mechanisms and the effect of heat treatment time and temperature on the superconductor properties are presented and compared to experiments. Within fairly wide limits, the considered parameters have low sensitivity to the heat treating conditions, so that process repeatability should be quite good. These results can be also be applied to stabilization of conductor with aluminum.         Super coupling currents in Rutherford type of cables due to longitudinal nonhomogeneities of dB/dt    A.P. Verweij and H.H.J. ten Kate Summary: In this paper it is shown that nonhomogeneities in the field sweep rate dB/dt along the length of a Rutherford cable provoke a nonhomogeneous current distribution during a field sweep. This process can be described by means of super coupling currents (SCCs) flowing through the strands over lengths far larger than the cable pitch. These SCCs can be characterised by a characteristic length, a characteristic time, and a propagation velocity. The dependence of these three parameters on the strand resistance and the contact resistance between strands is illustrated. Two longitudinal nonhomogeneities in dB/dt are considered which are present in accelerator magnets. Firstly, an increase in dB/dt from 0 to a certain value simulating that part of the cable where the cable enters the magnet field. Secondly, a longitudinal decrease in dB/dt which occurs mainly in the heads of the magnet. It is shown that in accelerator magnets a nonhomogeneous current distribution induced by the field sweep can not be avoided. However, it seems to be very difficult to estimate the amplitude of the effect.         Materials selection for ferromagnetic compensation in accelerator magnets    E.W. Collings and M.D. Sumption Summary: The magnetic hysteresis loops of Fe, Ni, and Ni-Cu in several geometrical forms were measured at 4.2 K. These materials were then evaluated for possible use as ferromagnetic correction elements in magnets wound from superconductive strands. The influences of demagnetization and cold work on the shape of the hysteresis loop were considered, and the saturation magnetizations, as well as the approach to saturation, were measured. Finally, several schemes were developed which would allow the selected alloys to be used for ferromagnetic compensation.         Development of Nb44wt%Ti 25wt%Ta based superconducting conductors for LHC magnets    G.K. Hoang, C.E. Bruzek, L. Oberli and D. Leroy Summary: A trial cable for LHC dipole inner layers made up of the Nb ternary alloy Nb44wt%Ti 25wt%Ta has been manufactured by GEC Alstrom Intermagnetics within the framework of a CERN development program. This cable is composed of 28 strands of 1.065 mm in diameter. The purpose of the study is: (i) to improve the superconducting behaviour of LHC cables at 1.9 K, the operating temperature of the Large Hadron Collider (LHC), and (ii) to evaluate the cabling feasibility of wires made with this alloy. Ic tests performed on wire samples before and after cabling at 4.2 K and 1.8 K show that at 4.2 K NbTi25wt%Ta wires exhibit lower Jc than those of the conventional binary alloy Nb47wt%Ti or those of a ternary alloy with only 15wt%Ta. But they have a larger magnetic field shift when cooled down from 4.2 to 1.8 K (about 1 T). The cabling of NbTi25wt%Ta wires presented no particular problem. Jc degradations due to cabling and evaluated on extracted strands are comparable to those observed on NbTi material. The performances achieved are reported and discussed in this paper.         Summary of the DNA SMES development program    G.W. Ullrich Summary: In 1987 the Strategic Defense Initiative Organization (SDIO) initiated a program at the Defense Nuclear Agency (DNA) to develop superconducting magnetic energy storage (SMES) as a short-duration, high-power source for a Free-Electron Laser-Directed Energy Weapon. SMES was also recognized as being able to fulfill the important civilian electric utility application of diurnal storage. In 1986 the Electric Power Research Institute (EPRI) had proposed an engineering test model (ETM) as the logical next step in SMES development. Since the military and civilian requirements for energy storage were similar, the SMES ETM development was proposed as a dual-use program from the outset. DNA was selected to manage the program because of its experience in managing the development of high-power nuclear-effects simulators. This paper summarizes the management results and conclusions of the two-phase SMES-ETM development program.         Review of the Bechtel team's SMES design and future plans for a technology demonstration unit    C.A. Luongo Summary: This paper traces the evolution in the Bechtel Team's SMES design over the last decade. Special emphasis is placed in the last two years when not only some design advances took place, but critical components were also built and tested. A major outcome of this latest phase is the realization that self-supporting SMES is more economical than the earth-supported approach advocated for many years. The paper concludes with a description of SMES-1, a 1 MWh/500 MW utility demonstration unit of the CICC-based self-supported SMES.         30 MW Babcock and Wilcox SMES program for utility applications    Xianrui Huang, S.F. Kral, G.A. Lehmann, Y.M. Lvovsky and Minfeng Xu Summary: Babcock and Wilcox (B&W) is working with Anchorage Municipal Light and Power (ML&P) to design; manufacture and install a 30 MW, 1800 MJ SMES system in Anchorage, Alaska. This will be the first mid-sized SMES system that will demonstrate full four-quadrant utility application. The system will consist of a superconducting magnet a power conversion system, a refrigeration system and a control system. This paper describes the general system, the utility applications, and the magnet and conductor design.         Design of a central solenoid model coil for the ITER magnet system    J.W. Wohlwend, S. Singh and D.B. Montgomery Summary: Martin Marietta and Westinghouse, in support of the US ITER (International Thermonuclear Experimental Reactor) Magnet Technology Development work at MIT, are developing designs for a model coil that will test the design concepts and manufacturing methods for the ITER Central Solenoid Magnets. The US is teamed with Japan in the development of a 13 T solenoid magnet that, combined with a separate superconducting insert coil, will test full size ITER concepts. The paper summarizes the design status and illustrates the manufacturing methods to be utilized in the fabrication of the US model coil components.         Poloidal field system for the Tokamak Physics Experiment    J.H. Schultz, R.D. Pillsbury Jr., A. Radovinsky, P.W. Wang, J. Citrolo, R.J. Bulmer, D. Lang, T. O'Connor, D. Slack, J. Zbasnik and L. Myatt Summary: The Tokamak Physics Experiment (TPX) at Princeton will be the first tokamak with an all superconducting poloidal field (PF) magnet system. The conductors are all cable-in-conduit (CICC) superconductors with a single conduit, similar to those in the International Thermonuclear Experimental Reactor (ITER). 10 of the PF coils use Nb/sub 3/Sn superconductor while 4 of them use NbTi. High noise initiation and disruptions demand the use of an advanced quench detection system.         An experimental generator using high temperature superconducting quasi-permanent magnets    R. Weinstein, R. Sawh and A. Crapo Summary: An experimental axial gap generator, with a 6 inch diameter rotor and quasi-permanent HTS magnets, was tested. A variable speed motor was used to rotate the rotor above a stator composed of copper wire wound in an 8 pole 3 phase configuration. The rotor and stator were both run in liquid nitrogen. A 3 phase variable resistor bank was the generator load. The HTS magnets were YBCO, each 2 cm in diameter and 1 cm thick, melt textured using a SmBCO seed, containing 60% excess Y, and about 1%Pt. They were not irradiated, and could trap maximum fields of 3500-4000 G. First, the HTS magnets were field cooled in a field of approximately 2200 G, provided by the stator while carrying 25 Amperes. The HTS magnets trapped about 1800 G. In this configuration, the generator was run for about one hour at speeds up to 2000 RPM, and developed a maximum power output of 33 Watts. Next the HTS magnets were warmed, and then zero field cooled. In this case, activation was accomplished by a /spl sim/15 ms pulse on the stator, providing 5000 G of pulsed field. The HTS magnets trapped about 2600 G. The generator was then run for about 1 hour at speeds up to 2265 RPM, and developed a maximum power output of just under 100 Watts.         Performance of MIT 10 MVA superconducting generator rotor    J.L. Smith Jr., J.L. Kirtley Jr., S. Sunder and S. Umans Summary: The MIT superconducting generator was run open circuit to a level of 12.9 kV. During this last test run the normally conducting armature winding flashed over short circuiting the machine from 12.2 kV. The superconducting rotor was stopped from 3600 RPM in less than 5 seconds. The superconducting field winding remained fully superconducting and the field current was manually reduced to zero. The complex eddy-current magnetic shield and the yoke structure for coil support proved to be of adequate design to protect the superconducting winding from the severe magnetic and the severe mechanical disturbances associated with the electrical fault in the armature. After the fault, the rotor was warmed to room temperature and run at full speed without any change in the balance. The problems encountered during construction and testing are given briefly, and the general conclusions drawn from the program are stated.         Stability characteristics of fully superconducting and damperless generator with excitation control in fault condition    Hui Chen and O. Tsukamoto Summary: A fully superconducting generator, which possesses both superconducting armature windings and superconducting field windings, has great potential merits to increase efficiency and decrease size and weight, compared with a partially superconducting generator that has normal armature windings and superconducting field windings. To obtain these merits, the warm and cold dampers should be omitted. However, omission of these dampers deteriorates the stability of the generator operation. In this paper, the authors present a simulation of a fully superconducting and damperless generator (FSDG) behaviour under fault conditions. Knowledge of behaviour under fault conditions is important for design of the superconducting windings of the FSDG. They show a possibility that the superconducting windings, both the armature and field, are quenched in a short circuit fault condition. They also show that excitation control allows the FSDG to stably recover from fault conditions, if the windings are not quenched, and that the current limiting devices to prevent the windings from quenches caused by a fault is necessary for a practical FSDG.         Superconducting linear synchronous motor for urban transport system    D.G. Pinatti, T.M. Souza and C.Y. Shigue Summary: The authors describe a superconducting linear synchronous motor (SLSM) for a high capacity urban transport system (10/sup 6/ passengers/day/line) able to climb a hill grade of 12%. The motor is composed of 26 poles installed below one wagon and is sufficient for traction of six wagons of 330 passengers each. The pole coil is a segmented race-track type 23 cm long, 140 cm wide, and 11.2 cm high. The conductor is composed of 14 transposed NbTi wires /spl phi/ 0.7 mm each, 5.04 mm/spl times/1.20 mm cross-section and Cu/SC ratio of 1.35. The current leads are made of high-T/sub c/ superconductor (melt textured growth YBa/sub 2/Cu/sub 3/O/sub 7-x/). These leads allow a pool cooling cryostat (2400 and of LHe) without an on-board refrigerator, and with one year holding time. The quench protection is made with cross-quench heater resistance placed within each coil. The limiting factor is the critical field of the NbTi and its substitution by Nb/sub 3/Sn should reduce the cost by a factor of 40%. Final cost of the SLSM is expected to be in the US$600,000 range. Due to the low speed (100 km/h), the suspension is made on conventional bus type tyres.         Recent development progress of 70 MW class superconducting generators    Y. Nakagawa, M. Kazumori, T. Ichikawa, S. Ohshima, B. Ikeda, Y. Matsunobu, Y. Yagi, A. Ueda and T. Kitajima Summary: This paper describes recent results of the R&D carried out on 70 MW class superconducting generators, known as model machines, by Super-GM in Japan, according to an 11-year period program conducted since FY 1988.         A 62 MJ superconducting MHD dipole    F. Negrini and R. Penco Summary: A five-year national program on superconducting (SC) magnets technology has been carried out in Italy. The aims of the research activities were: the design and the construction of a SC prototype magnet (2 m active length) with stored energy of 62 MJ, using fabrication technologies suitable for MHD industrial size magnets; and the reference design of a SC demonstrative magnet (8 m active length). The prototype is designed to produce more than 5 T field on axis, with 5% field uniformity in the channel cross section. During the last months, the winding of the SC prototype at ANSALDO-GIE workshop in Genova has been completed utilizing about 9 km of NbTi copper stabilized CIC ("rope in a pipe" type). The most interesting aspects of the fabrication process, including the vacuum impregnation of the 7.5 tons coils in one step, the main problems in the construction of large cable in conduit magnets, and the characteristics of the product obtained are reported and discussed in the paper.         MHD linear generator modelling    A. Geri, A. Salvini and G.M. Veca Summary: The performance of typical magnetohydrodynamic (MHD) linear generators are evaluated as function of the excitation magnetic field profile. Using a three dimensional (3D) lumped parameter model, able to simulate all major physical MHD energy conversion phenomena, a parametric analysis has been pointed out for various saddle shaped superconducting (SC) coils. For each type of MHD linear generator (Faraday, Hall and diagonal connected generator) the output electrical power has been correlated to the magnetic field characteristics and it has been compared with an ideal flat magnetic field profile in order to quantify the decay of the energy conversion efficiency.         Monitoring of superconducting magnet system using fuzzy theorem    Y. Uriu, A. Ninomiya, Y. Kanda, T. Ishigohka, Y. Takahashi, N. Koizumi, M. Nishi and H. Tsuji Summary: For the monitoring of large superconducting magnets like those in a nuclear fusion reactor, it is necessary to make decisions integrating data gathered by numerous sensors. Here, the authors propose such a new method using a fuzzy theorem. This method utilizes a number of variables such as fundamental membership functions. These fundamental membership functions are incorporated in the fuzzy theorem and generate one diagnostic factor called the "dangerous factor". They apply this method to the monitoring of an experimental superconducting magnet CS-2. The handheld-type PC based system is installed on the superconducting magnet system for online monitoring tests. The result shows that dangerous factor synthesized by this method can express the quench margin of the magnet.         Transient thermal analysis and quench detection characteristics of the ITER TF and CS coils    E.A. Chaniotakis, J.P. Freidberg, J. McCarrick and A. Shajii Summary: The toroidal field (TF) and the central solenoid (CS) coils of ITER experience a variety of transient heating loads. During normal operation, the conductor in the TF coil experiences nuclear heating, whose magnitude is a function of the plasma operating conditions. In addition, the TF coils experience minor heating due to AC losses and the friction between the support plates. The heating in the CS coil is mainly due to AC losses which is significant during plasma start-up and shut-down. Due to the pulsed operation, and because of the long length of the flow paths (/spl sim/800 meters), steady state conditions are not established during a single pulse. In order to determine the operating margins, time dependent analyses of both the TF and the CS coils are performed under various heating conditions and over many cycles. Quench detection methods based on flow measurements at the inlet and outlet of the flow paths have to distinguish between "normal" and quench related flows. Extensive analyses of the flow signals under different operating and quench conditions show that, with the proper differencing the signal due to quench can be extracted.         Universal scaling laws for quench and thermal hydraulic quenchback in CICC coils    A. Shajii, J.P. Freidberg and E.A. Chaniotakis Summary: A set of universal scaling relations is presented describing the propagation of quench in CICC (cable-in-conduit superconducting magnet) magnets. Four distinct types of behavior are possible depending upon the length of the coil and the magnitude of the quench induced pressure rise. The boundaries separating these regions can be simply expressed in terms of L/sub q/ the initial quench length, and J the stabilizer current density, the two parameters likely to vary during standard operation. The phenomenon of thermal hydraulic quenchback (THQB) is also considered. It is shown that the conditions for the onset of THQB can also be cast as a set of universal scaling relations and easily superimposed on the quench diagram.         Quench analysis of multisection superconducting magnet    O. Ozaki, Y. Fukumoto, R. Hirose, Y. Inoue, T. Kamikado, Y. Murakami, R. Ogawa and M. Yoshikawa Summary: The numerical quench simulation code includes the effect of the filament coupling loss. We apply this simulation code to two multisection high field magnets. In this paper we describe the modified quench simulation code which includes the effect of filament coupling loss and make comparisons between the experimental and analytical results.         Quench simulation and thermal diffusion in epoxy-impregnated magnet system    Y.M. Eyssa and W.D. Markiewicz Summary: We have developed a new computer code that addresses quench simulation and analysis of a magnetically coupled epoxy-impregnated superconducting magnet system. The new computer code contains several new provisions: (1) it includes the effect of AC loss from the field variations in the winding due to field change because of the fast current transfer between the magnetically coupled solenoids; and (2) simultaneous solution of the propagation velocities in all directions in each coil by solving the thermal diffusion equation in the three directions (tangential, radial and axial). In addition to the above new features, the code solves for the currents, voltage, temperature distribution, and resistance of each coil as function of time. Thermal simulation of the protection switch and the quenching heaters is part of the new code.         US contributions to the development and calibration of quench detectors for the ITER QUELL    S. Pourrahimi, W.C. Guss, J.V. Minervini, D.B. Montgomery, N.T. Pierce, J.H. Schultz, S.P. Smith and S. Ezekiel Summary: The ITER QUELL (quench experiment on long length) experiment calls for the development and demonstration of new methods of quench detection for cable in conduit (CIC) superconductors. These will directly monitor temperature and pressure changes within the CIC. The use of single mode optical fibers is being investigated for measurement of temperature during a quench. A full-length pressure sensor/switch consisting of two conducting strips enclosed in a flattened stainless steel capillary has also been developed. Above a threshold He pressure of about 1 MPa, tube walls will deflect enough to short the otherwise open strips to trigger a current relay switch and also reflect microwave pulses that are generated at the strips ends. These signals can independently indicate the occurrence and the location of a quench. These new sensors will be integrated with more conventional instruments which include co-wound insulated voltage sensors placed inside the CIC, strain gauge pressure transducers, and flowmeters to measure quench parameters.         On the numerical studies of quench in cable-in-conduit conductors    L. Bottura and A. Shajii Summary: The ability of accurately modeling the process of propagation in superconducting magnets wound with cable-in-conduit conductors (CICC) is an important key to the study of quench detection and the protection of large magnet systems for fusion applications (e.g. the ITER project). The main goal of this paper is to define proper convergence criteria that need to be satisfied in order to obtain a satisfactory numerical solution to the problem of quench propagation in CICC. It is shown that erroneous results are obtained when such criteria are not satisfied.         Critical current, quench and stability of a BSCCO/Ag high field shim coil    H.W. Weijers, Y.S. Hascicek and S.W. Van Sciver Summary: A pancake wound coil of BSCCO/Ag was built and characterized in background fields up to 17.5 T. Hysteresis in J/sub c/(H), voltage-current characteristics well beyond J/sub c/, and quench properties were investigated. The coil was developed as a shim coil for a high field superconducting solenoid operating at 4.2 K.         The construction and performance of BSCCO 2212 coils for use in liquid nitrogen at 64 K on an iron yoke in demonstrator devices    R.G. Jenkins, H. Jones, Ming Yang, M.J. Goringe and C.R.M. Grovenor Summary: The construction of 6 HTS coils from composite tapes of a silver alloy dip-coated with BSCCO 2212 is described. Data are presented on the coil critical currents at temperatures over the range 4.2 K to 77.3 K, including the results of a measurement in liquid neon. A small magnet constructed from two of the coils generated a peak field of 0.434T at 4.2 K. A "demonstrator" device is described in which the cells are mounted on an iron yoke, are immersed in liquid nitrogen refrigerated to 64 K using a novel technique, and provide ampere-turns to generate a magnetic field in the air gap between two room temperature pole-pieces. This apparatus is intended for use in a programme of research to investigate the controllability of superconducting magnets in attractive magnetic levitation applications.         Performance of pancake coils of parallel co-wound Ag/BSCCO tape conductors in static and ramped magnetic fields    S.W. Schwenterly, J.W. Lue, M.S. Lubell, M.S. Walker, D.W. Hazelton, P. Haldar, J.A. Rice, J.G. Hoehn Jr. and L.R. Motowidlo Summary: Critical currents are reported for several Ag/BSCCO single-pancake coils in static magnetic fields ranging from 0 to 5 T and temperatures from 4.2 K to 105 K. The sample cells were co-wound of one to six tape conductors in parallel. Since the closed loops formed in such an arrangement could lead to eddy current heating or instability in changing fields, one of the coils was also tested in helium gas, in fields ramped at rates of up to 1.5 T/s. For these quasi-adiabatic tests, at each temperature the transport current was set just below the critical value for a preset static field of 3.3 or 4.9 T. The field was then rapidly ramped down to zero, held for 20 see, and then ramped back up to the original value. The maximum observed temperature transient of about 1.7 K occurred at 9 K, for a field change of 4.75 T. Transients became negligible when immersed in liquid helium. Above 30 K, the transients were below 1 K. These results give confidence that parallel co-wound HTSC coils are stable in a rapidly-ramped magnetic field, without undue eddy current heating.         Development of Bi-2223 HTS high field coils and magnets    P. Haldar, J.G. Hoehn Jr., Y. Iwasa, H. Lim and M. Yunus Summary: The powder-in-tube approach was successfully used to fabricate silver clad Bi-2223 in >100 m lengths of mono and >800 m lengths of multifilament tape. The tapes were wound into pancake and layer coils using the 'wind and react' as well as the 'react and wind' technique. The coils and magnets were characterized in the Hybrid III magnet and in a cryocooler at the FBNML, MIT. A 'wind and react' magnet generated a maximum self field of 2.6 T, at liquid helium (4.2 K), liquid neon (27 K) and liquid nitrogen (77 K) temperatures, respectively. A magnet generated over 1.0 T with a background field of 20 T at 4.2 K. A smaller magnet cooled to 20 K with a two-stage cryocooler has demonstrated 0.8 T in a 40 mm room temperature bore.         Fabrication of high T/sub c/ coils from BSCCO 2212 powder in tube and dip coated tape    W. Dai, K.R. Marken Jr., S. Hong, L. Cowey, K. Timms and I. McDougall Summary: Engineering considerations for the production of small HT/sub c/ coils for commercial high current applications have been evaluated. Part of this study involved investigations of the conditions under which coils are wound, heat treated and potted in order to reproduce, in lengths exceeding 50 m, the critical current density (J/sub c/) which can be attained in short samples of a few cm in length. Individual pancake coils were evaluated by testing their 4.2 K superconducting current capacity in the presence of an applied magnetic field up to 10 T. The performance of each coil was compared to the J/sub c/ capacity predicted from short sample J/sub c/ testing on samples of a few cm length. Coils were then stacked to form prototype magnets and the field generated by the magnet was measured using a Hall probe.         Development of superconducting magnets using Bi-2212/Ag tapes    N. Tomita, M. Arai, E. Yanagisawa, T. Morimoto, H. Kitaguchi, H. Kumakura, K. Togano, T. Kiyoshi, K. Inoue, H. Maeda, K. Nomura and J.C. Vallier Summary: Several pancake type superconducting coils were fabricated using Bi-2212/Ag tapes prepared by the combination of continuous dip-coating process and melt-solidification and tested in various temperatures and bias fields. A small Bi-2212/Ag double stacked pancake coil(13 mm/spl phi/ (inner bore)/46.5 mm/spl phi/ (outer diameter)) was used as an insert magnet of a conventional superconducting magnet system. In the bias field of 20.9 T, the generated field of the Bi-2212/Ag coil was of the Bi-2212/Ag coil was 0.9 T, at the I/sub c/ of 310A (criterion 10/sup -13/ /spl Omega/m), in the saturated superfluid helium temperature (/spl sim/1.8 K). Thus, this superconducting magnet system achieved generation of magnetic field of 21.8 T in the full superconducting state. A larger Bi-2212/Ag double stacked pancake type magnet (20 mm/spl phi/ (inner bore)/spl times/94 mm/spl phi/ (outer)) was also fabricated. The generated fields of the magnet at 4.2 K in 0 and 20 T bias fields were 2.6 T (I/sub c/=385A(10/sup -13/ /spl Omega/m)) and 1.08 T (I/sub c/=160 A(2/spl times/10/sup /spl times/13/ /spl Omega/m)), respectively. At about 20 K, in helium gas, the generated field of the magnet was 1.53 T (I/sub c/=225A(10/sup -13/ /spl Omega/m)).         Magnetic shielding effect by complex structure with HTS pipes and ferrite powder on HTS current lead    K. Nakamura, T. Kasuga, Y. Abe and E. Inukai Summary: This paper presents the magnetic shielding characteristics of a complex structure with multiple high-Tc superconductors (HTS) coaxially superposed and ferrite powder padding, and its effect on the critical current increase of a HTS current lead. A model HTS current lead is inserted into the complex structure and cooled by LN2. The magnetic flux density in the innermost HTS pipe with and without the ferrite powder, and the critical current of the current lead were measured and the various complex structures were evaluated.         Magnetic shielding and trapping properties of BPSCCO superconducting tubes    V. Plechacek, J. Hejtmanek, D. Sedmidubsky, K. Knizek, E. Pollert, Z. Janu and R. Tichy Summary: Tubular superconducting magnetic shields were prepared from the (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10+x/ superconductor. A single tube of wall thickness of only 1.8 mm traps magnetic flux density of 30 mT at the temperature T=77.3 K and 60 mT at 63.2 K, while for a coaxial system of five tubes of overall thickness 9.6 mm, it increases to 70 mT at 77.3 K. A shielding factor as high as 5/spl times/10/sup 6/ was found for the superconducting tube of inner diameter d=22 mm and length and inner diameter ratio l/d=4.6.         Numerical simulation of current-quenching phenomena for high Tc YBaCuO superconducting thin films    T. Nakamiya, T. Ikegami and K. Ebihara Summary: The current quenching characteristics of a YBaCuO thin film (1 /spl mu/m thick, 2 mm wide and 8 mm long) on MgO are studied numerically by solving the heat flow equation. The finite element method is applied to solve the equation considering the temperature dependence of the resistance and thermal conductivity, and the effect of the convection coefficient. Currents of different wave forms were fed to the thin films for a few tens of milliseconds in liquid nitrogen to measure the temporal resistance. The substrate temperature at the bottom is kept at 77.3 K. When a ramp current of dI/dt=83.5 A/s (duration: 17 ms) is applied to the current terminals of the YBaCuO thin film, the temperature starts to increase after 10 ms, and reaches a maximum temperature of 155 K (maximum resistance: 7.3 /spl Omega/) at 17 ms for a convection coefficient of 1.0 W/cm/sup 2/ K. The calculated results are compared with experimental data obtained from the resistive characteristics of a YBaCuO superconducting thin film quenched by a current.         The VAMAS intercomparison on the upper critical field measurement in Nb-Ti wire    K. Tachikawa, S. Koyama, S. Takahashi and K. Itoh Summary: The intercomparison on the upper critical field measurement in the Nb-Ti wire (NIST-SRM 1457) has been performed through the VAMAS (Versailles Project on Advanced Materials and Standards) TWA 6 activity. The homogeneity in the H/sub c2/ of the wire is fairly good, while the coefficient of scatter in the H/sub c2/ intercomparison is about 0.60%. The scatter in high field measurement may cause that in critical current measurement at high magnetic fields. Effects of several factors on the H/sub c2/ of the Nb-Ti wire have also been studied. The coiled specimen shows slightly lower H/sub c2/ than the straight sample. The H/sub c2/ of the wire shows an appreciable anisotropy with respect to the direction of applied field.         Report on the second VAMAS AC loss round robin-magnetization measurement of low-frequency hysteretic loss    E.W. Collings, M.D. Sumption, K. Itoh, H. Wada and K. Tachikawa Summary: We report on the results of the 2/sup nd/ VAMAS (Versailles Project on Advanced Materials and Standards) intercomparison program on low-frequency (hysteretic) AC loss measurements. Two sets of multifilamentary NbTi strands were subjected to round-robin testing. In an initial series of tests, samples in various forms were measured mostly by vibrating-sample- and SQUID magnetometry. Considerable scatter was noted especially in the small-filament-diameter AC-loss data. In a study of measurement accuracy, a supplementary round-robin compared the results of VSM measurement of a given pair of copper-matrix samples. In the light of all the results, factors contributing to AC loss error are discussed and recommendations are made concerning the specification of future round-robin AC-loss testing.         VAMAS critical current round robin test on a 2212 BSCCO Ag-sheathed tape    K. Itoh, Y. Murakami, M. Yuyama and H. Wada Summary: Aiming at the establishment of a reliable critical current, I/sub c/, a measurement method for oxide superconductors, a round robin test (RRT) has been implemented in Japan in the framework of VAMAS (Versailles Project on Advanced Materials and Standards), using a 2212 BSCCO Ag-sheathed tape conductor. In this RRT each participant received two pre-instrumented and pre-measured specimens and one freestanding specimen. Measurements were made at 4.2 K and magnetic fields ranging from 0 to 10 T. One of the pre-instrumented specimens was also routed among participants as a RRT specimen. Together with the RRT specimen, a superconductor I-V simulator was circulated to intercompare the I-V measurement set-ups used at participant labs. Measurements on pre-instrumented specimens have shown that I/sub c/ of Ag-sheathed tapes is sensitive to the heat cycle, which may be attributed to the deformation of the oxide superconductor by swelling and/or to the formation of cracks inside the oxide layer.         USA interlaboratory comparison of superconductor simulator critical current measurements    L.F. Goodrich, J.A. Wiejaczka, A.N. Srivastava, T.C. Stauffer and L.T. Medina Summary: An interlaboratory comparison of critical current (I/sub c/) measurements was conducted on the superconductor simulator, which is an electronic circuit that emulates the extremely nonlinear voltage-current characteristic of a superconductor. These simulators are high precision instruments, and are useful for establishing the integrity of part of a superconductor measurement system. This study includes measurements from participating US laboratories, with NIST as the central, organizing laboratory. This effort was designed to determine the sources of uncertainty in I/sub c/ measurements due to uncertainties in the measurement apparatus, technique, or the analysis system. The participating laboratories measured the superconductor simulator with a variety of methods including DC and pulse. This comparison indicated the presence of systematic biases and higher variability at low voltages in the I/sub c/ determinations of the measurement systems. All critical current measurements at a criterion of 10 /spl mu/V on the I/sub c/ simulator were within 2% of the NIST value for nominal critical currents of 2 and 50 A. These results could significantly benefit superconductor measurement applications that require high-precision quality assurance.         First VAMAS USA interlaboratory comparison of high temperature superconductor critical current measurements    L.F. Goodrich, J.A. Wiejaczka, A.N. Srivastava, T.C. Stauffer and L.T. Medina Summary: We conducted an interlaboratory comparison of critical current (I/sub c/) measurements on Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ tapes (2223). This study includes measurements from six participating US laboratories, with NIST as the central, organizing laboratory. A number of specimens were prepared with different degrees of instrumentation to isolate sources of variability. Most of the specimens were pre-measured by NIST to reduce uncertainties due to sample variability. Different specimen routing patterns among the laboratories were implemented to isolate sources of variability due to the specimen's measurement history. This study is similar to other VAMAS (Versailles Project on Advanced Materials and Standards) intercomparisons being performed in Japan and Europe and is the first internationally cooperative interlaboratory comparison of HTS (high temperature superconductors) I/sub c/ measurements. These are the first steps towards developing standard measurement procedures for HTS.         Characterizing the S/N transition of VAMAS HTS samples    H.W. Weijers and S.W. Van Sciver Summary: As a part of a VAMAS program, the S/N transition of short sample HTS conductors were studied for a range of fields and temperatures. This paper discusses the characterization of typical and damaged samples at 4.2 K and 0 T. Attention is given to the calculation of n-values and the first derivative of the V-I curves. Also, the measurement setup is explained in some detail.         Anomalous quench propagation in superconductors under fast current decrease    A.A. Pukhov, A.L. Rakhmanov, V.S. Vysotsky and V.N. Tsikhon Summary: The normal transition of a superconducting NbTi-CuNi multifilamentary wire under fast transport current decrease (dI/dt<0) is studied both experimentally and theoretically. The normal zone propagation velocity v(t) is measured at.         Estimation method of stability for multi-strand superconducting cables under partial current distribution    M. Ono, Y. Wachi, T. Hamajima, H. Yamaguchi, Y. Sawada, K. Yamamoto and T. Fujioka Summary: The stability margin of CIC multi-strand superconducting cables under partial current distribution is affected by electrical resistance among the strands. This means that the stability is governed by the current sharing process among the strands. The achievement of high stability against partial current distribution will be realized by rapid current transfer to the other strands rather than by thermal diffusion of Joule heating to helium. A simplified electrical circuit model, that is a distributed constant circuit for two strands, simulating the current sharing process between strands, is proposed to estimate the stability. The results of the stability analysis, clarify the limiting condition to maintain stability. The circuit constants governing the sharing process can be investigated from the frequency properties of a characteristic impedance measured with CICC short samples. These results are confirmed with experimental results of stability tests under partial current distribution. The proposed estimation method is viable.         Heat transfer characteristics of the supercritical helium in a cable-in-conduit conductor    Y. Wachi, M. Ono and T. Hamajima Summary: To study the thermal stability of a forced-cooled superconducting coil with a cable-in-conduit conductor (CICC), it is important to measure the steady-state heat transfer characteristics of the supercritical helium in the narrow channel like a CICC at various conditions. The measured heat transfer coefficient is compared with one calculated by the Giarratano correlation and other studies. The results obtained show that measured values for turbulent flow scatter widely and the values for laminar flow are 1.5-1.8 times larger than those calculated from Nu=4.36. The stability of a CICC is discussed with the relation between the Stekly's stability limit and the measured heat transfer coefficient.         On stability of multistrand cables with insulated or highly resistive matrix strands    V.S. Vysotsky, V.N. Tsikhon, Y.A. Ilyin and A.V. Gavrilin Summary: The stability of multi-strand superconducting cables or cables-in-conduit is degraded by rapid changes in current or field (ramp rate limitation or current degradation). The maximum achievable AC current is significantly less then the sum of DC critical currents of strands. Measurements of the dependence of quench current on ramp rate were made for one, two, and three strand cables. Samples had different strand types and lengths. It was shown that although the theory of thermomagnetic instability explains single strand performance very well, it does not explain the reduction of quench current observed in multi-strand cables. The influence of joint resistance between cable strands and current leads is shown to be the most probable reason for the reduction.         Stability experiments on long lengths of CICC's    L. Bottura, D. Ciazynski, J.L. Duchateau and A. Martinez Summary: One of the driving issues in the design of superconducting magnets for application in fusion is their response to electromagnetic perturbations (i.e. AC losses) on characteristic conductor lengths of several meters. The question to be answered is whether the stability of the conductor subjected to energy deposition over such lengths will be degraded compared to the values measured for short initial heated lengths as the analysis based on 1-D computational models tends to indicate. Samples of subsize cable-in-conduit conductors (CICC's) have been built, with typical sample and heated length in the range of 10 to 35 m. Tests on these samples have started, and the authors report here on the first results of this experimental campaign.         New method of current distribution studies for ramp rate stability of multistrand superconducting cables    V.S. Vysotsky, M. Takayasu, M. Ferri, J.V. Minervini and S.S. Shen Summary: The ramp rate limitation phenomena were studied using local field sensors to observe the intrinsic processes within the cable. Sensitive miniature Hall sensors and small pick-up coils placed around cable-in-conduit superconductor were used to measure local magnetic fields and field derivatives associated with currents in the cable. Using this method, both fast jumps and slow changes in local magnetic fields at different conditions mere observed. First jumps occured during ramping background magnetic field and may indicate a fast current redistribution processes. Slow changing of local fields may be associated with current loops closed through the current lead joints. Such current loops may also indicate the nonuniformity of current distribution in the cable strands. The new method is a promising tool for future investigations of stability of multistrand cables.         Stability against transient disturbances in cable-in-conduit conductors cooled by supercritical helium    Y.M. Lvovsky Summary: The stability of cable-in-conduit superconductor (CICC) is analyzed for transient disturbances applied to a strand. The study is focused on the effects of thermal contact between strands and transient heat transfer in supercritical helium, including thermal expansion to neighboring voids. The process of normal zone growth from strand to strand was numerically modeled using a 2-D approximation. Stability margins were determined for the well cooled and poorly cooled regimes. Interstrand contacts as well as longitudinal helium flow involve more strands and helium voids, thus significantly improving CICC stability. The effect of helium thermal expansion, transient heat conduction and shape of disturbance is discussed.         Stability analysis of the TPX toroidal field coil    R.L. Wong Summary: The energy stability margin of the TPX/TF conductor has been calculated as a response to heat pulses with short initial quench zones (IQZ=10, 20 cm for 4, 20, 100 ms), and with long initial quench zones (IQZ=2.28, 4.53 m for 20, 50, 100 ms). The short IQZs approximate ramp-rate induced heating, and the long IQZs approximate heating from a plasma disruption. These IQZs are centered in the bore inner leg of the double pancake, where the operating field and temperature are maximum. Energy margin stability curves are plotted as a function of current. The stability of the 10 cm IQZ differs from that for the 20 cm IQZ by less than 20%. Similarly the stability of the 2.28 m IQZ differs from that for the 4.53 m IQZ by less than 20%. However the stability of the short IQZs (10 and 20 cm) is about twice as high as that of the long IQZs (2.28 and 4.53 m). The friction in the long IQZs prevents the conversion of heat to work by helium expansion during the pulse. At the 33.5 kA design current, the minimum calculated stability margin with short IQZs is 390 mJ/cc. The minimum calculated stability margin with long IQZs is 205 mJ/cc. A comparison of the stability margin with the available enthalpy (short IQZs) and with the available internal energy (long IQZs) shows that the conductor utilizes the available helium energy well.         Comparison of the calculated and measured stability of a NbTi cable-in-conduit conductor    R.L. Wong and C.T. Yeaw Summary: Calculated curves of cable-in-conduit conductor (CICC) energy stability margins vs. current are compared to experimental curves obtained at Oak Ridge National Laboratory for NbTi single triplex conductors. The conductors ranged in length from 1.8 m to 4.8 m, and had no imposed helium flow. The initiating heat pulse was applied for 16.7 ms over the entire conductor length. The calculated stability curves display the large decrease in energy margin from the low current and high energy margin "well-cooled" stability region, to the high current and low energy margin "ill-cooled" region that was determined experimentally. The calculated "limiting current" of 250 A (boundary between the ill-cooled and well-cooled regions) also agrees with experiment. The multi-valued stability margins measured for lengths of 3.1 and 3.8 m could not be obtained by the computer model. Excluding the multiple stabilities, the calculated margins are generally 30% lower than the experimental values. The decrease in energy margin in the ill-cooled region was found to be due to the low critical to operating temperature difference (2.2 K at 250 A). This prevents an initiating pulse in the ill-cooled region from being able to generate significant Joule heating without quenching, limiting the energy margin.         Influence of current distribution on quench process in noninsulated AC multi-strand superconducting cables    M. Tsuda, K. Okazaki, H. Hashizume and A. Ishiyama Summary: In AC multi-strand superconducting cables, AC quench current is much less than that of DC. This AC quench current degradation is caused by AC loss, mechanical damage by cabling, nonuniform current distribution among strands due to self and mutual inductances between strands, and different electrical resistivity at the joint between superconducting strands and current lead. In this paper, the current distribution and the thermal behavior of noninsulated 7- and (6+1)-strand cables applying AC transport current are analyzed and the influence of contact electrical resistivity on the current redistribution and the thermal diffusion in the quench process are investigated.         SHE3D-a code for the three dimension steady-state helium-cooled CICC conductors    Pei-Wen Wang Summary: The superconducting magnets needed for the next generation of fusion tokamaks such as ITER and TPX must operate under steady-state conditions. The conductors are wound in pancakes and several pancakes are usually required for each winding pack. Supercritical helium is used to cool the conductors, and carry away the heat from such sources as neutrons and eddy currents. The analysis of the steady-state heat removal is very important in the magnet design. A code, SHE3D (steady-state helium-cooled conductor in 3D), has been developed for this purpose. This code includes the turn-to-turn and pancake-to-pancake heat conduction for steady-state conditions. The entire winding pack can be treated for a self-consistent study that includes several flow channels, different heat loads in each channel, and different magnetic fields (which impacts the critical current). Typical results for TPX toroidal field coil cooling are presented.         Minimization of the induced current effects in the shields of SC coils in EDS-MAGLEV trains    M. Andriollo, G. Martinelli, A. Morini and A. Scuttari Summary: In magnetically levitated transport systems of the electrodynamic type, eddy-currents in the shield of the on-board superconducting coils are caused by the harmonics of the magnetic field produced by the on-ground coils, in particular by the reaction field of the levitation coils. The paper presents a method to optimize the geometrical sizes of both the superconducting and the levitation coils, with the aim to minimize the field harmonic content on the shield. The method is based on the iterative application of analytical expressions of the flux density produced by the levitation coils. As an example of application, a given configuration is optimized according to the proposed technique; the shield eddy-current losses are calculated by means of a 3D FEM code for both the starting and the optimized configurations and the results are compared.         A conceptual design of a superconducting magnet for MAGLEV using a Bi-based high-Tc tape    S. Yokoyama, K. Shimohata, T. Inaguchi, T. Takeuchi, T. Kim, S. Nakamura, S. Miyashita and F. Uchikawa Summary: A conceptual design of a superconducting magnet for MAGLEV using a Bi-based high-Tc superconducting tape ((BiPb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 8/-Ag) is studied. In this study, the structure of conductor and coil, AC loss, stability, current lead, persistent current switch, cryostat structure and cooling system are estimated. The characteristics of the design are as follows: (1) the superconducting coil is cooled by a refrigerator at 20 K and is operated by persistent mode; (2) the coil is constructed by 6 pieces of double pancake coils, and each pancake coil is graded by changing conductor size; (3) the temperature rise of the coil is about 2 K due to AC loss; and (4) the superconducting stability is very high.         Combined system of levitation, propulsion and guidance for Maglev vehicles using high-temperature superconducting magnetic potential well    S.B. Kuznetsov Summary: A hybrid electrodynamic (ED) propulsion system intended for 480 km/hr and 100 kN thrust is described using an integral system of ED repulsive suspension and ED lateral guidance of the vehicle on a common primary structure. The machine is intended to operate as a hybrid synchronous-induction motor with the Maglev vehicle carrying the primary structure; the guideway is passive. An array of 20 K HTSC superconducting excitation coils on-board the vehicle yields a magnetic potential well over a 50 mm airgap with high lateral restoring forces sufficient to stabilize and levitate a 75 tonne vehicle. The proposed cryogenic support system uses gaseous helium cooling. Test results are provided from an active guideway 1/16th scale Maglev using a 28 mm airgap and normal conducting excitation.         Engineering prototype of a superconducting flywheel for long term energy storage    H.J. Bornemann, A. Tonoli, T. Ritter, C. Urban, O. Zaitsev, K. Weber and H. Rietschel Summary: We built a flywheel system with superconducting magnetic bearings. The bearing consists of six melt-textured YBCO pellets mounted inside a continuous flow LN/sub 2/ cryostat. A disk measuring /spl phi/ 190 mm/spl times/30 mm was safely rotated at speeds up to 15000 rpm. The disk was driven by a high speed three phase synchronous homopolar motor/generator. Maximum energy capacity was 4.8 Wh, maximum power was 1.5 kW. The dynamic behavior of the prototype was tested, characterized and evaluated with respect to axial and lateral stiffness, damping, decay torques (bearing drag), vibrational modes and critical speeds. Experimental data were found to be in agreement with a structural damping model. Rotor unbalance together with the hysteretic nature of the superconducting magnetic bearing gave a significant contribution to the overall losses. At a background pressure of 6/spl times/10/sup -4/ mbar, the coefficient of friction (drag-to-lift ratio) was measured to be /spl mu/=9/spl times/10/sup -6/. The experiments demonstrate the applicability of superconducting magnetic bearings in highly efficient, kinetic energy storage systems.         Design of superconducting magnetic bearings with high levitating force for flywheel energy storage systems    Z. Xia, Q.Y. Chen, K.B. Ma, C.K. McMichael, M. Lamb, R.S. Cooley, P.C. Fowler and W.K. Chu Summary: Hybrid superconducting magnetic bearing (SMB), using YBCO high temperature superconductors (HTS) coupled with permanent magnets, has been implemented into a flywheel energy storage (FES) system prototype. The hybrid SMB design uses permanent magnets to levitate the rotor weighing 19 kg and superconductors to stabilize the inherently unstable magnet-magnet interactions. The SMB bearings are brought into action under convenient field-cooled conditions. Spin-down performance of the constructed FES prototype was tested under a moderate vacuum.         Low rotational drag in high-temperature superconducting bearings    J.R. Hull, T.M. Mulcahy, K.L. Uherka and R.G. Abboud Summary: Bearings consisting of permanent magnets stably levitated over high-temperature superconductors exhibit low rotational drag and have the potential to enable high-efficiency flywheel energy storage. The coefficient of friction /spl mu/ for such storage systems is derived as a function of bearing parameters and is shown to be an appropriate figure of merit to describe bearing losses. Analysis shows that values of /spl mu/ <10/sup -6/ enable flywheel standby losses <0.1%/hr for high-speed flywheels. A vacuum-chamber experimental apparatus has been constructed to measure values of /spl mu/ for various experimental bearing designs. Experimental values for /spl mu/ at low velocity have been as low as 3/spl times/10/sup -7/ for an 89-mm-diameter ring permanent magnet stably levitated over an array of melt-textured Y-Ba-Cu-O. An important loss mechanism occurs from eddy currents induced in the rotating magnet due to the discrete nature of the superconductor array.         Development of an active superconducting magnetic bearing    T.A. Coombs, A.M. Campbell and D.A. Cardwell Summary: The potential use of YBa/sub 2/Cu/sub 3/O/sub 7/ as an active component in a magnetic bearing is being investigated. Measurements are being made of the load bearing capacity and related stiffnesses in comparison to predictions from the critical state model. Although the load bearing capacity is high and increases with the square of the magnetic field trapped, the stiffness is low. We report on a novel design concept to overcome this problem which uses superconducting bulk materials. In bulk materials where the magnetic field is produced by persistent currents trapped in the superconductor this option is not available. However the available force is a function of the flux density and the area over which it is applied. Thus even if the flux density remains constant then changes in available force may be made by changing the active area of the bearing i.e. increasing the area of overlap between the magnetic components. Using this method active control may be achieved using bulk materials and the inherently low stiffness of the materials is no longer a problem.         Superconducting bearing systems using high Tc superconductors    M. Komori, A. Tsuruta, S. Fukata and T. Matsushita Summary: To realize the practical use of superconducting bearings, three types of superconducting bearing systems using high Tc superconductors are constructed. This paper describes static characteristics such as load capacities of the bearings and dynamic characteristics of the rotors. Spin-down tests of the rotors are performed to evaluate dynamics of the systems. One of three rotors of the bearing systems is very well self-centered in the speed range not exceeding 63000 RPM. The displacements of the rotor are smaller than 30 /spl mu/mp-p (peak to peak) except near the critical speeds.         High temperature superconducting bearings for lunar telescope mounts    M. Lamb, Ki Bui Ma, R. Cooley, D. Mackey, Ruling Meng, Ching Wu Chu, Wei Kan Chu, P.C. Chen and T. Wilson Summary: A telescope to be installed on the lunar surface in the near future must work in a cold and dusty vacuum environment for long periods without on site human maintenance. To track stars, the drive mechanism must be capable of exceedingly fine steps and repeatability. Further, the use of lightweight telescopes for obvious economic benefits burdens the requirement for stable support and rotation. Conventional contact bearings and gear drives have numerous failure modes under such a restrictive and harsh environment. However, hybrid superconducting magnetic bearings (HSMB) fit in naturally. These bearings are stable, light, passive, and essentially frictionless, allowing high precision electronic positioning control. By passive levitation, the HSMB does not wear out and requires neither maintenance nor power. A prototype illustrating the feasibility of this application is presented.         Fundamental study on high Tc superconducting magnetic bearings for flywheel system    S. Nagaya, N. Hirano, M. Takenaka, M. Minami and H. Kawashima Summary: Basic quasi-static tests of superconducting magnetic bearings are carried out using YBa/sub 2/Cu/sub 3/O/sub 7-/spl alpha// (YBCO) and Nd-Fe-B permanent magnets. In the thrust type tests, two kinds of c-axis oriented YBCO bulks are used. These YBCO bulks are produced by a melt process using a seed crystal. The measured maximum repulsion pressure between the YBCO and the magnet between the YBCO and the magnet is 0.14 MPa at 77 K under the zero-magnetic-field cooling condition. This repulsion pressure, which is a top level value, enables the authors to consider the application of the superconducting magnetic bearings. The attractive forces between the YBCO and the magnet under the field cooling condition are also measured at 77 K. In the radial type tests, the force between a ring-shaped YBCO bulk and a shaft combined with multi-ring magnets are measured in the liquid nitrogen. A simplified formula is proposed to evaluate the repulsion force. As an application of the superconducting magnetic bearings, a flywheel system is preliminary designed for the energy storage of one kilowatt-hour. The flywheel, which is made of fiber reinforced plastic, is a ring shape having an outer diameter of 600 mm and a height of 100 mm.         Control aspects of superconducting magnets for magnetic suspensions and bearings    R.M. Goodall, C.J. MacLeod, A.A. El-Abbar, A.M. Campbell, H. Jones and R.G. Jenkins Summary: The paper describes some theoretical and experimental considerations aimed at identifying the main characteristics of high Tc/sub /superconducting magnets for use in controlled applications such as magnetic suspensions and bearings. The theoretical model is formulated to represent the requirements necessary for such applications, and some experiments reinforce this by assessing the effects of periodic variations in both excitation and reluctance over a range of frequencies. In this way a clear understanding can be obtained of the factors which affect the losses in the superconductors, and also the drive voltage requirements are identified for different operating conditions.         Testing of a superconducting spectrometer dipole    A.F. Zeller, S. Bricker, L. Morris, D. Pendell, R. Swanson, R. Fontus, B.M. Sherrill, H. Laumer, B. Zhang, D. Sanderson, J.C. DeKamp, P. Johnson and J. Caggiano Summary: A superconducting dipole magnet for use as spectrometer element has been constructed and is presently being mapped. The 75 ton dipole has a negative curvature side and a 15 cm gap. The cryostable coil produced a central field of 1.6 T at a current of 436 A. A second identical magnet is presently under construction. The authors describe the assembly and testing of the magnet.         Ballooning of a thin superconducting solenoid for particle astrophysics    Y. Makida, K. Anraku, J. Suzuki, A. Yamamoto, M. Imori, T. Yoshida, K. Yoshimura, I. Ueda, T. Saeki, H. Matsunaga, S. Orito, M. Motoki, M. Nozaki, N. Yajima and D.L. Righter Summary: A thin superconducting solenoid was launched by using a large balloon up to an altitude of 36.5 km in Northern Canada in the summer of 1993 as a core facility for the cosmic ray spectrometer, BESS. The magnet was excited up to 1.0 T in persistent current mode on the ground and was launched being attended with 2.7 G shocks. After 17 hours successful flight, it was discharged on the sky and made a mild descending and landing by using a parachute for recovery. The magnet was safely operated without problems during flight in 1993 and contributed to a second observation in the summer of 1994.         Control of field uniformity for a large superconducting storage ring magnet    G.T. Danby and J.W. Jackson Summary: A 1.45 Tesla, 14.2 meter diameter "superferric" magnet is in an advanced stage of construction at Brookhaven National Laboratory. This magnet will be used to store muons for a planned ultra-precise measurement of their anomalous magnetic moment g-2. This measurement requires a magnetic field uniformity of 1 PPM with a knowledge of the field over the muon orbits to 0.1 PPM. The methods built into the design to produce ultra-high field uniformity are described. Large deviations from the ideal circularly symmetric uniform shape of the iron flux path are required to accommodate transfer lines and superconducting current leads, as well as apparatus for beam injection. Shimming methods to correct for the perturbations due to these large holes are presented. The pole pieces consist of 36 closely fitting 10/spl deg/ arc sections butted together to produce a very good approximation to a continuous 360/spl deg/ ring magnet. However, in the case of a possible quench of the superconducting coils, significant eddy currents will be induced which will circulate within the confines of each 10/spl deg/ pole piece. At the great precision required, these eddy currents may leave very small but significant aberrations in the field even after they decay away, because of slight changes in the orientation of the magnetization. Surface coil possibilities to correct for this effect are described.         Magnetization effects from the g-2 inflector magnet superconductor    M.A. Green and W. Meng Summary: The g-2 muon storage ring at Brookhaven National Laboratory will have a 1.7 meter long superconducting inflector magnet for injection of the muon beam into the storage ring. The field within the inflector is designed to be nearly zero. The inflector bucks out the main dipole field, but generates little or no stray field of its own. A portion of the field that remains is the field that is generated by circulating currents in the inflector magnet superconductor. Because the magnetization field has a different structure from field generated by the transport current, the magnetization field can adversely affect the field quality within the muon storage ring good field region. Correction of the effects of inflector superconductor magnetization and its effect on the good field region in the storage ring is discussed.         The superconducting inflector dipole for the muon g-2 storage ring    F. Krienen, G.T. Danby, W. Meng, C. Pai, W.B. Sampson, K.A. Woodle, M.A. Green, A. Yamamoto and H. Hirabayashi Summary: A muon storage ring for the g-2 experiment at Brookhaven National Laboratory will have a DC superconducting inflector magnet for injection of the muon beam. This inflector locally bucks out the 1.45 tesla storage ring dipole field, so that the muon beam enters the ring tangentially as close as possible to the equilibrium orbit. The g-2 experiment requires the knowledge of the magnetic field over the muon orbits to a precision of 0.1 ppm. The inflector has nested dipole coils of opposite polarity so that it cancels its external magnetic flux and generates very little stray field. Nevertheless the residual field would affect the homogeneity of the storage ring magnetic field. A method of using a multilayer superconducting (SC) composite sheet surrounding the inflector to further reduce the fringe field has been proposed. This sheet should prevent the stray field due to the inflector from affecting the field quality of the muon storage region. In developing this new type of air-core septum magnet, a shortened SC prototype inflector was built in Japan at KEK. It has been used for testing the superconducting performance (in KEK, BNL) and the fringe flux shielding (in BNL). Some of the test results are presented.         Transient stress analysis during quench of MRI magnets    D.A. Gross, E.T. Laskaris and C. Minas Summary: A quench simulation model is analyzed by means of control theory for optimal computational efficiency relative to a complex network of coupled shells. The authors describe the superconducting magnet configuration and the time domain aspects. They then discuss quench transient analysis and force transient analysis. The control theory analysis derived identifies an optimal computation efficiency for the numerically intense problem of 3D quench analysis with coupled circuits. This scheme of numerical time step integration has wider applicability.         Passive shimming of the superconducting magnet for MRI    A. Belov, V. Bushuev, M. Emelianov, V. Eregin, Yu. Severgin, S. Sytchevski and V. Vasiliev Summary: The method of passive shimming of homogeneous magnets is presented. The simple regular configuration of the thin iron strips is used. Positions of the strips are optimized by computer simulation and independent of the field distribution, i.e. remain the same despite magnet modification. The variable parameter for field correction is the number of strips on each position. Contribution of shims to the field distribution is defined by computer simulation. The number of strips is calculated by a regularized least square method taking into account point field measurements in the working volume. This method was successfully used for correction of the field of the 0.3 T superconducting magnet for MRI with large initial unhomogeneities. The results are presented.         AC losses in high T/sub c/ superconductors    A.M. Campbell Summary: The losses in high T/sub c/ superconductors do not differ in principle from those in low T/sub c/ materials, and the same calculations can be used. However it is necessary to allow for the granularity of the materials and the high aspect ratio of the conductors. This paper derives simple, if approximate, expressions for calculating the losses in the most important cases for practical purposes. These are the use of BSCCO tapes in magnets and cables at power frequencies. The predictions of elliptical and thin strip models are compared and it is found that an elliptical geometry agrees best with the experimental results. It is also found that the voltage measured in a transport measurement depends on the position of the contacts and that if an unambiguous loss measurement is required it is necessary to include the flux outside the sample in the voltage measurement loop.         AC loss measurement of the 45-T hybrid/CIC conductor    B.J.P. Baudouy, K. Bartholomew, J. Miller, S.W. Van Sciver and A.B. Oliva Summary: The results of calorimetric measurements of the AC loss in a cable-in-conduit (CIC) conductor under development for the a 45T hybrid superconducting outsert magnet are reported. The technique is unique in that the absorbed energy is determined by measurement of the temperature rise in the He II contained in the conductor. The sample is located in a separate cryostat and placed in the bore of a 7 T superconducting dipole magnet. A change in transverse field results in heating which produces an easily measurable temperature increase of the helium surrounding the conductor. Samples of Nb/sub 3/Sn CIC conductor developed for the high field portion of the 45 T hybrid magnet system have been measured. The time constant measured for this sample is compared to analysis based on a combination of hysteresis and eddy current losses.         Contact resistance and cable loss measurements of coated strands and cables wound from them    M.D. Sumption, H.H.J. ten Kate, R.M. Scanlan and E.W. Collings Summary: Calorimetric and magnetic studies of AC loss have been performed on 11-strand Rutherford cables made from multifilamentary strands with a variety of coatings. Interstrand contact resistance (R/sub c/) measurements supplemented these studies. R/sub c/s were deduced from the M-H determined eddy current loss as a function of ramp rate for four superconducting wires arranged in a rectangular geometry and put under a predetermined strain. It was found that: (1) the dominant factor which determines the R/sub c/ for uncoated strands is the level of surface oxidation (even for solvent cleaned strands); (2) strands can be de-oxidized either by an HCl etch or a vacuum anneal; and (3) strand coatings add significantly to the contact resistances of un-oxidized strands. It is concluded that contact resistance, and hence cable loss, is largely determined by the surface condition of the strands rather than the area ("spoon size") of the interstrand contact.         AC behaviour of full size, fusion dedicated cable-in-conduit conductors in SULTAN III under applied pulsed field    B. Blau, I. Rohleder, G. Vecsey, L. Bottura, P. Bruzzone and H. Katheder Summary: The coupling current losses of a full size, fusion dedicated Nb/sub 3/Sn cable-in-conduit superconductor are measured as a function of the transverse load in the SULTAN III test facility. Applying a broad range of transport current (up to 56 kA) and background field (up to 12.1 T), the change of the transverse resistance is observed through the shift of the O-crossing in the pick-up coil voltage. Despite the difficulty to extract useful information from the signal, the role of the strand Cr plating as resistive barrier is experimentally assessed under operating conditions. The friction factor of the conductor is also evaluated from pressure drop measurements.         AC V-I characteristics of Ag sheathed PbBi2223 tapes up to 10 kHz: phenomena and interpretations    Y. Yang, T. Hughes, C. Beduz, D.M. Spiller, Z. Yi and R.G. Scurlock Summary: The self-field AC V-I characteristics of PB2223 silver sheathed superconducting tapes were measured at 9 different positions across the tape at 77 K and 65 K between 47 Hz and 10 kHz. The significant difference found between the centre and the edge was interpreted as the result of the complex geometry of tapes. The implication of this difference to the measurement of the total losses is discussed. Considerable contributions from eddy current losses in the silver sheath were also found for frequencies above 200 Hz.         Current, induction profiles and hysteretic losses in high-Tc superconducting tapes    C. Levillain, P. Manuel and P.G. Therond Summary: Current, induction profiles and hysteretic losses have been calculated in the framework of numerical simulations for high Tc superconducting tapes in transverse magnetic field (self-field effects, anisotropic field dependence of the critical current density are taken into account). It appears that hysteretic losses are widely influenced by both the tape width and the field component perpendicular to the tape width, except for field nearly parallel to the tape.         AC losses of Ag-(Bi,Pb)SrCaCuO-2223 tapes in combination of transverse external magnetic field and transport current    M. Ciszek, B.A. Glowacki, S.P. Ashworth, A.M. Campbell and J.E. Evetts Summary: The authors present the results of measurements of the AC transport (self-field) and magnetic losses on silver sheathed (Bi,Pb)SrCaCuO-2223 tapes prepared by the powder in tube method. In the frequency range 30-540 Hz the transport current losses are hysteretic in nature. Losses arising from AC external magnetic field (frequency range 65-207 Hz, amplitude up to 60 mT) are compared with losses generated by AC transport currents. The measured transport loss voltage depends strongly on the position of the potential taps on the surface of the tapes. Losses due to combined AC applied magnetic fields and transport currents are also reported.         Electric field and losses in BSCCO-2223/Ag tapes carrying AC transport current    J. Paasi, M. Polak, P. Kottman, D. Suchon, M. Lahtinen and J. Kokavec Summary: Electric field and losses in single layer coils wound of 0.75 m long multifilamentary BSCCO-2223/Ag tapes carrying AC transport current have been studied at both 4.2 K and 77 K in the frequency range from 0.01 Hz up to 100 Hz, with the main effort at 50 Hz. Current amplitudes (I/sub p/) ranged from i=I/sub p//I/sub c/=0.5 to 1.3, critical current (I/sub c/) determined by the standard 1 /spl mu/V/cm static electric field criterion. I/sub c/ of coil 1 was 15 A at 4.2 K and 3 A at 77 K. Losses due to the wide resistive transition of the coils were found to dominate over self-field losses even well below i=1. Therefore the total losses in the whole applicable i range could not be described well by equations based on the critical state model.         Superconducting DC/AC magnetic system for loss and magnetization experiments operating up to 50/60 Hz    M. Polak, J. Pitel, M. Majoros, J. Kokavec, D. Suchon, M. Kedrova, J. Kvitkovic, H. Fikis and H. Kirchmayr Summary: Loss and magnetization measurements provide very complex information on the electromagnetic properties of superconductors. Measuring methods frequently require DC magnetic field with AC superposition at various frequencies. The simplest system to produce this field seems to be a coaxial magnet system consisting of an outer DC coil with an inner AC insert. However, this configuration results in strong coupling between the AC and DC coils. As a result, the DC coil performance is strongly degraded. The authors present a solution of this problem, based on the use of two coaxial AC coils instead of one. The geometrical configuration which they developed reduces the coupling of AC coils with the DC coil almost perfectly. Using the described concept, the authors projected, realized and tested a DC/AC superconducting magnet system which can produce a DC magnetic field of up to 4 T with AC superposition varying from 0.4 T (B/sub DC/=4 T) up to 1.1 T (B/sub DC/=0 T) and frequency up to 50/60 Hz.         The change of coupling losses in aluminum-stabilized superconductors due to the Hall effect    F. Sumiyoshi, S. Kawabata, H. Ono, T. Kawashima, T. Mito, N. Yanagi, K. Takahata, T. Satow and J. Yamamoto Summary: The change of coupling losses in aluminum-stabilized superconductors due to the Hall effect is investigated experimentally and numerically. The Hall effect is here taken to be an interaction between the inter-strand coupling current and the external DC magnetic field. The loss measurement of the R&D conductor for the helical coil of the Large Helical Device is carried out under the coexistence of the transverse and the longitudinal magnetic fields. The measured coupling loss of the real conductor induced by the changing transverse magnetic field is increased by the existence of the longitudinal DC field. These loss features are compared with those by numerical analysis, based on the two dimensional finite element method, of a real conductor with complex cross-sectional structure.         Influence of sample geometry on amplitude of eddy current oscillation in Rutherford-type cables    A.A. Akhmetov, K. Kuroda and M. Takeo Summary: Interstrand eddy current induced in the samples of flat two-layer superconducting cables of finite length by ramping up uniform magnetic field are found to be periodic. Corresponding energy losses are compared with those calculated for eddy currents being uniform along the sample length. Dependence of amplitude of eddy current oscillations on the sample geometry is considered.         Properties of proximity effect and filament coupling in NbTi wires    K. Yasohama, S. Nagano, Y. Kubota and T. Ogasawara Summary: Filament coupling induced by the proximity effect was studied through AC susceptibility measurements an Cu-matrix NbTi multifilamentary wires. The sample wires having different interfilamentary spacings ranging from 0.35 to 1.04 /spl mu/m and various twist pitches were prepared from the VAMAS (Versailles Project on Advanced Materials and Standards) reference sample H-1, which has a filament number of 931. The measurements were carried out in each of the two different field directions, parallel and perpendicular, to the wire axis. It has been found that the value of perpendicular field to suppress the proximity effect coupling is two orders of magnitude larger than that of the parallel field. In the perpendicular field, the twist of the wires affects the occurrence of the coupling: the filaments couple at higher temperature and higher field with longer twist pitch. On the contrary, the twist pitch dependence of the coupling has not been observed in a parallel field. In addition, the effect of transport current on the coupling has been examined.         Dependence of self field AC losses in AC multifilamentary composites on phase of external AC magnetic field    S. Fukui, O. Tsukamoto, N. Amemiya and I. Hlasnik Summary: The authors have measured the self magnetic field AC losses of a typical AC multifilamentary superconducting wire in an AC transverse external magnetic field at 50 Hz. The experimental results show that the self field AC losses are much higher than the transverse field AC losses and strongly depend on the phase difference between the transport current and the background field. They derive a theory to estimate the dependence of the self field AC losses on the phase of the external field based on the critical state model. In the paper, the measured loss characteristics are compared with the theoretical results. The theoretical model explains the measured loss characteristics.         Experimental evaluation of AC losses in superconducting multifilamentary wires for 50/60 Hz use exposed to a magnetic field with arbitrary angle with the wire axis    H. Kanetaka, H. Ueda, Y. Eguchi, M. Iwakuma, K. Funaki, M. Takeo, K. Yamafuji, S. Miyake, T. Kumano and M. Ichihara Summary: In multiple twisted superconducting cables exposed to an external AC transverse magnetic field, a component of magnetic field parallel to the strand axis due to the twisting structure of the cables causes an additional AC loss (longitudinal AC loss) in the strands. The authors experimentally evaluate the longitudinal AC loss by an equivalent measurement with short samples of the strands exposed to an oblique magnetic field to the strand axis. The total loss obtained at 60 Hz was equivalent to a direct sum of the hysteresis loss, the coupling-current loss for the transverse component and the additional loss for the longitudinal one. In triple twisted superconducting cables composed of insulated strands, measured AC losses could be also quantitatively explained in the same manner as for the short samples. These results suggest that the longitudinal loss may be dominant in an AC magnetic field with relatively large amplitude along with the coupling-current losses inside and among strands. The authors also discuss an optimum condition for the twist pitch of the strand to reduce the total AC loss of the strands in the cable.         Pressure drop measurements of prototype NET and CEA cable-in-conduit conductors (CICCs)    R. Maekawa, M.R. Smith and S.W. Van Sciver Summary: The pressure drop of two prototype cable-in-conduit conductors (CICCs) were measured. The NET conductor is a conventional type CICC, while the CEA conductor has a central flow channel to reduce hydraulic impedance. The pressure drop measurements were conducted with helium at temperatures ranging from 2 K to 4.7 K, and pressure from the saturated vapor pressure to in excess of 3 bar. Computer image analysis was used to estimate the flow cross sectional area and wetted perimeter of the conductors. The data are expressed in terms of a classical friction factor, and compared with previous experimental results.         Thermohydraulics of CICC's with central cooling passage    L. Bottura Summary: The cable-in-conduit conductors for ITER will have a "central cooling hole", a low impedance flow channel whose purpose is to decrease the pressure drop per unit length. The helium flow and the response to temperature transients of such an arrangement has unique features compared to those of the simpler CICCs without central cooling hole. The purpose of this paper is to discuss these features and to propose a model for the description of the compressible thermohydraulics of the ITER conductors. Some typical applications of the model proposed (transient cooling of a conductor length in a magnet, quench evolution) are also shown as an example.         Transversal conductivity in conductors of "cable in conduit" type    P.I. Dogosheev, G.G. Svalov, V.E. Sytnikov, I.V. Podyablonskaya and G.K. Matshueva Summary: This paper offers a method for measuring and selecting conductivities between the strands and wires and displays the measurement results for transversal electrical conductivity between elements of a cable twisted of superconducting wires based on niobium-tin in bronze matrix. Sub-cables of 2, 3 and 4 wires and cables of 4/spl times/3, 4/spl times/4, 3/spl times/4/spl times/4 and 4/spl times/4/spl times/3 constructions are considered. The coupling losses in CIC-type cables consist of several hundreds of strands are strongly influenced by the transverse resistance. The presented method allows the measurement and identification of the contact resistance between strands, sub-cables and multi-strands core and conductor conduit. Some experimental results for multiply twisted and compacted cables and presented. It is shown that transverse conductivity varies within the range from 10/sup 4/ to 10/sup 9/ (Ohm*m)/sup -1/ and for typical cases, conductivity between the conduit and multistrand core was much less then between the strands and sub-cables.         Manufacture and verification testing of low-resistance Nb/sub 3/Sn joints for Cable-in-Conduit Conductors    T.A. Painter, J.R. Miller, J. Bascunan, P. Riley and A.L. Devernoe Summary: Two coils using Nb/sub 3/Sn Cable-in-Conduit Conductor (CICC) will be manufactured for assembly into the 45 T Hybrid Magnet at the National High Magnetic Field Laboratory (NHMFL). The design calls for low-resistance joints on the order of 1 nanoohm. Several joints were fabricated at Intermagnetics General Corporation (IGC) and tested at the Francis Bitter tested at the Francis Bitter National Magnet Laboratory (FBNML) to qualify the fabrication procedures and specifications. Two types of joints were tested: "praying hands" and "shorted-loop" joints. The joint design, fabrication procedures, modeling and tests are discussed. Test results are compared with the requirements of the 45 T system.         Development of a superconducting joint technique between CIC conductors for poloidal coil of large helical device (LHD)    S. Hanawa, Y. Wachi, K. Shibayama, J. Shibuya, S. Mizumaki, T. Yamamoto, K. Nakamoto, T. Kai, K. Takahata, J. Yamamoto, T. Satow and O. Motojima Summary: A solid state bonding technique been developed for the large superconducting joint of LHD poloidal coils. Low electrical resistance, high superconducting stability and compactness are required for the joints between pancake coils. All NbTi strands of cable-in-conduit (CIC) conductors were jointed directly and at one time by the proposed technique. From the critical current test with the real scale joint model, it is shown that quench current of this joint is about 1/3 times of the conductor critical current. This paper describes the main points in manufacturing the joint and evaluation of the quench current.         GEM detector conductor manufacturing experience    N.N. Martovetsky, J.R. Pace, P.J. Reardon, D.E. Richied, R.J. Camille Jr., P.G. Marston, B.A. Smith, G.A. Deis, J.S. Bohanan, J.H. Gertsen, J.L. Heck, L.N. Howell, S.C. Robinson and H. Marti Summary: Feasibility studies and manufacturing experience on the GEM Magnet conductor are presented, including all components-NbTi strand, cable, conduit manufacture, cable pulling, and aluminum sheath application.         Design chart of high temperature superconducting gas cooled current leads    K. Maehata, T. Nishioka, K. Ishibashi and M. Takeo Summary: General design equations derived from one dimensional energy balance equations are solved to evaluate generalized characteristics of gas cooled current leads which are made of high temperature superconducting (HTSC) material. Design parameters of the conductor and the cooling channel are combined into a single general cooling parameter with the consideration of laminar flow. Generalized characteristics of HTSC current leads, namely the heat flow from the cold end of the leads, the geometrical dimension of the conductor and the pressure drop of the cooling gas are represented in a design chart with the general cooling parameter. Thermal runaway of the conductor is analyzed for various geometrical dimensions in the case of stoppage of the cooling gas with the consideration of the quench propagation. The temperature rise time works as a criterion for determining the geometrical dimension according to the criterion, the heat flow from the cold end is estimated to be less than 0.1 mW/A.         Large current high T/sub c/ superconducting rods for current lead applications    D. Ponnusamy, Z. Li and K. Ravi-Chandar Summary: The high critical temperature and low thermal conductivity of ceramic superconductors make them suitable for current leads in low T/sub c/ magnets. The plastic extrusion process was applied for the fabrication of YBaCuO and BiSrCaCuO rods for this application. The platelet morphology of BiSrCaCuO was utilized to process rods with a high degree of preferred orientation, through a combination of plastic extrusion and cold isostatic pressing. Rods with consistent current capacities of few hundred amperes over 15 cm have been fabricated. The critical currents of these rods were measured at various temperatures and magnetic fields. Other related aspects such as contact resistance, mechanical properties and degradation due to thermal cycling have also been evaluated.         HTS current lead using a composite heat pipe    M.A. Daugherty, F.C. Prenger, D.D. Hill, D.E. Daney and K.A. Woloshun Summary: This paper discusses the design and fabrication of HTS current leads being built by Los Alamos to supply power to a demonstration HTS coil which will operate in a vacuum cooled by a cryocooler. Because vapor cooling is not an option for this application the leads must be entirely conductively cooled. In the design of HTS current leads for this type of application, it is desirable to intercept part of the heat load at an intermediate temperature. This thermal intercept or connection must be electrically insulating but thermally conductive, two mutually exclusive properties of most candidate solid materials. To achieve this end we incorporate a composite nitrogen heat pipe, constructed of conducting and nonconducting materials, to provide efficient thermal communication and simultaneously, electrical isolation between the lead and the intermediate temperature heat sink. Another important feature of the current lead design is the use of high Jc thick film superconductors deposited on a nonconducting substrate to reduce the conductive heat leak through the lower portion of the lead. Two flexible electrical conductors are incorporated to accommodate handling, assembly and the dissimilar expansion coefficients of the various materials.         Testing of a prototype high temperature superconducting current lead    J.L. Wu Summary: A prototype helium vapor-cooled current lead employing a ceramic high temperature superconductor was designed and tested. The lead which has a nominal current rating of 1 kA consists of copper and a ceramic superconductor sections and was designed for operation in 300 K/4.2 K temperature range. A single monolithic bismuth-based superconductor (BSCCO-2212) was used in the superconductor section. Extensive testing of the current lead was carried out to determine its performance such as steady-state boil-off rates at various operating currents, transient characteristics of the lead under zero-flow condition, and the effects of repetitive current cycling. At 1000 A operating current, the lead was found to require a steady-state helium vapor cooling flow rate equivalent to a liquid helium boil-off rate of 0.98 l/hr, an over 40% reduction from the conventional all copper lead. Cut-off of helium vapor flow for 230 seconds poses no overheating problem and no performance degradation was observed after 1000 cycles of repetitive current cycling between 0 and 1000 A. A very low contact joint resistance, 17 n/spl Omega/ for carrying 1000 A, was also observed at the 4.2 K lead terminal.         Current cycling test on HTSC for Westinghouse current leads    J.A. Selvaggi, J.L. Wu and J. Bock Summary: To evaluate the reliability of high temperature superconducting current leads for repetitive current ramping operations such as in a magnetic separator, a ceramic high temperature superconductor with its copper terminals was subjected to current cycling tests in liquid nitrogen. The superconductor, a cylindrical rod of BSCCO-2212 fabricated by a melt cast process, has an initial J/sub c/ (B=O) of 970 A/cm/sup 2/ at 77 K and a total contact joint resistance for both terminals of 2 /spl mu//spl Omega/ in the current range of 100 to 500 A. Due to power supply limitation, the cycling current magnitude was set at 50 A. The cycling rate was 1 cycle per minute, 30 seconds on 30 seconds off. After approximately 80000 cycles and 250000 cycles, measurements of J/sub c/ and contact joint resistance were repeated. No degradation in either J/sub c/ or contact joint resistance was detected. The testing and the test results are discussed in detail.         Optimization of high-temperature superconductor current leads    S.Y. Seol, J.R. Hull and M.-C. Chyu Summary: Methods to improve the performance of high-temperature superconducting current leads are analyzed. Designs are considered that are inherently safe from burnup, even if the lead enters the normal state. The effect of a tapered lead that takes advantage of the increase in critical current density with decreasing temperature will decrease helium boiloff by about a factor of two for an area ratio of four. A new concept, in which Ag powder is distributed in increasing concentration from the cold end to the hot end of a sintered YBCO lead, is shown to have comparable performance to that of leads made with Ag-alloy sheaths. Performance of the best inherently safe designs is about one order of magnitude better than that of optimized nonsuperconducting leads. BSCCO leads with Ag-alloy sheaths show improved performance for Au fractions up to /spl ap/3%, after which increases in Au fraction yield negligible improvement in performance.         Design of a high-temperature superconductor current lead for electric utility SMES    R.C. Niemann, Y.S. Cha, J.R. Hull, C.M. Rey and K.D. Dixon Summary: Current leads that rely on high-temperature superconductors (HTSs) to deliver power to devices operating at liquid helium temperature have the potential to reduce refrigeration requirements to levels significantly below achievable with conventional leads. The design of HTS current leads suitable for use in near-term superconducting magnetic energy storage (SMES) is in progress. The SMES system has an 0.5 MWh energy capacity and a discharge power of 30 MW. Lead-design considerations include safety and reliability, electrical and thermal performance, structural integrity, manufacturability, and cost. Available details of the design, including materials, configuration, performance predictions, are presented.         Performance evaluation of high-temperature superconducting current leads for micro-SMES systems    R.C. Niemann, Y.S. Cha, J.R. Hull, W.E. Buckles, B.R. Weber and S.T. Yang Summary: As part of the US Department of Energy's Superconductivity Technology Program, Argonne National Laboratory and Superconductivity, Inc., are developing high-temperature superconductor (HTS) current leads for application to micro-SMES systems. Two 1500 A HTS leads have been designed and constructed. A component performance evaluation program was conducted to confirm performance predictions and/or to qualify the design features for construction. The evaluations included HTS characteristics, demountable electrical connections, and heat intercept effectiveness. The performance of current lead assemblies is being evaluated in a zero-magnetic-field test program that included assembly procedures, tooling, and quality assurance; thermal and electrical performance; and flow and mechanical characteristics. The leads were installed in a liquid helium test cryostat and connected at their cold ends by a current jumper. The leads were heat intercepted with a cryocooler.         Conceptual design of a 20-kA current lead using forced-flow cooling and Ag-alloy-sheathed Bi-2223 high-temperature superconductors    R. Heller and J.R. Hull Summary: High-temperature superconductors (HTSs) consisting of Bi-2223 HTS tapes sheathed with Ag alloys are proposed for a 20-kA current lead for the planned stellarator WENDELSTEIN 7-X. Forced-flow He cooling is used, and 4-K He cooling of the whole lead, as well as 60-K He cooling of the copper part of the lead, is discussed. Power consumption and behavior in the event of loss of He flow are given.         Composite reaction textured Bi-2212 twin current lead structures    D.R. Watson, M. Chen, D.M. Glowacka, N. Adamopoulos, B. Soylu, B.A. Glowacki and J.E. Evetts Summary: Monolithic twin Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub x/ (Bi-2212) conductors have been fabricated on MgO-LiF, stainless steel and Macor substrates for current lead applications. The composite reaction texturing (CRT) method gives considerable flexibility in design; a composite aligned MgO whisker/Bi-2212 polymer processing route can be shaped before reaction to match the critical current to the system temperature profile. Leads have been designed for conduction cooled zero field 4 K and 77 K. At 4 K the critical current density (J/sub c/) is in excess of 10/sup 5/ A cm/sup -2/, at 77 K J/sub c/ is self-field limited and varies between 10/sup 3/ A cm/sup -2/. Leads 10-20 cm in length were designed for currents of 200 and 1000 A with thermal conduction losses of less than 0.05 W and flexural loads greater than 10 N.         Design and test of the prototype high T/sub c/ current leads for the Large Hadron Collider orbit correctors    A. Ballarino and A. Ijspeert Summary: The Large Hadron Collider (LHC) will need some 800 superconducting magnets to correct the orbit of the particle beams. These magnets will be individually powered and each needs a pair of current leads to the ambient temperature. To minimize the heat loss through these leads, the magnets have been designed for a very low current of about 25 amperes and the leads could be made with high T/sub c/ material. A theoretical study by the authors (see Adv. Cryog. Eng., vol.39, 1994) investigated different types of high T/sub c/ leads. Since then, a prototype has been built which combines a low heat loss with an extremely simple design. The design, the test set up and the results are described in this paper.         YBa/sub 2/Cu/sub 3/O/sub x/ low loss current leads    N.M. Alford, T.W. Button, S.J. Penn and P.A. Smith Summary: The low thermal conductivity of high-temperature superconducting ceramic YBCO (<1 Wm/sup -1/ K/sup -1/ at 77 K) in comparison with normal metal such as copper (/spl sim/480 Wm/sup -1/ K/sup -1/ at 77 K) suggests their use as current leads. The authors demonstrate a modular lead design which has very low resistance contacts and where the power dissipated at an arbitrarily chosen current level of 100 A is several orders of magnitude lower than that dissipated by the normal metal leads presently used in such applications. This suggests that significant cost savings may be made resulting from the reduced liquid helium boil-off rate. The leads are fabricated by novel ceramic processing techniques which give a high degree of uniformity and reproducibility, and strengths in flexure approaching 200 MPa for the individual elements, the highest values reported.         Application of high-T/sub c/ superconductors in aluminum electrolysis plants    M. Runde Summary: The electric power system in an aluminum electrolysis plant has several features that may advocate use of superconducting technology: high power, low voltage, system compactness, direct current, and substantial conductor cost and losses per meter. Two case studies where the cost of conventional busbar conductors is compared with the predicted cost of a future nitrogen-cooled high-amperage superconductor based on Ag/BSCCO tapes are carried out. To be an attractive alternative the investment and capitalized operational costs of a superconducting line should not exceed USD 70 per meter per kiloampere rating. Simplified estimates of cost and properties of a superconducting cable show that these requirements are very hard to satisfy, even if long lengths of Ag/BSCCO tapes with operating current densities as high as 50 kA/cm/sup 2/ become available.         Development of a 10 kA-class high-Tc superconducting bus bar    T. Ando, T. Isono, H. Tsuji, T. Kato, T. Hikata and K. Sato Summary: In order to investigate the applicability of high-Tc materials for bus lines between magnets and power supplies in a fusion reactor, a 10 kA-class bus bar has been fabricated and tested at 77 K. The bus bar consists of 10 conductor units which are prepared by stacking 250 Bi-2223 superconductor tapes which are made by a powder-in-tube method. The 10 conductor units are installed into the grooves on a decagonal FRP structure and the current for each unit conductor is carried in the opposite direction for the current of neighboring unit conductor to reduce the self magnetic field. The bus bar was immersed in liquid nitrogen and was successfully operated up to 10.3 kA with the alternative go-and-return structure.         Critical current measurement unit utilizing Bi-based oxide superconducting current leads and cryocoolers    T. Hasebe, T. Tsuboi, K. Jikihara, S. Yasuhara, J. Sakuraba, M. Ishihara and Y. Yamada Summary: A measurement unit has been developed to investigate the dependence on temperature and magnetic field of superconducting cable critical current without the use liquid helium or liquid nitrogen. A test specimen, which is tested using the four probe method, is cooled by a Gifford-McMahon (GM) type cryocooler to a temperature of 20 K to 90 K in a vacuum vessel. Transporting direct current, up to 500 A, is supplied to the specimen through the Bi-based oxide superconducting current leads. The advantages of utilizing oxide superconducting current leads are that the leads have low thermal conductivity, and also that the leads create no Joule heating effect, so the heat input to the sample is minimized. The external magnetic field of up to 3 T, which is applied to the specimen, is generated by a superconducting magnet which also uses Bi-based oxide superconducting current leads and is also cooled by a GM cryocooler. Detail design of the unit, the results of operating test and an example of the measurement result on the Bi-based oxide bulk specimen are presented in the paper.         Cryogen free Nb/sub 3/Sn magnet, operated at 9.5 K with High Tc BiSrCaCuO (2212) current leads    L. Cowey, P. Cetnik, K. Timms, P. Daniels, J. Mellors and I. McDougall Summary: A superconducting Nb/sub 3/Sn magnet has been operated in the absence of liquid cryogen utilising the cooling power of a 2 stage Gifford-McMahon cryocooler. The magnet generated 2.0 T in a 17 cm bore at a current of 145 A and a temperature of 9.5 K. Current was supplied via high T/sub c/ BiSrCaCuO (2212) current leads. The magnet demonstrated long term stability and was successfully quenched without any damage to the system; recovery was complete within 40 minutes.         An overview of RF superconductivity research    H. Padamsee Summary: RF superconductivity has become an important technology for particle accelerators. Structures providing more than 100 million volts (MV) have been installed in accelerators for heavy ions and operated at gradients between 2.5-5 MV/m for greater than 10/sup 5/ hours. More than 1300 MV have been installed in electron accelerators and operated at gradients between 3-10 MV/m in excess of 3/spl times/10/sup 4/ hours. Beam currents up to 40 mA are supported in continuous operation. New applications are forthcoming, some demanding higher accelerating gradient, others the capability to support high beam currents. Substantial progress has been made in understanding gradient limitations and inventing techniques are now in hand to reach 25 MV/m. For the next linear collider in the TeV energy range, there are many compelling attractions to use superconducting cavities. For high current application, the beam-cavity interaction can be reduced by using a few high gradient cavities with large beam apertures. Low impedance structures are being developed. In a breakthrough, one of these was successfully tested with a beam current of 220 mA.         CEBAF's SRF cavity manufacturing and some performance limitations    J.F. Benesch and J. Mammosser Summary: Construction of the CEBAF (Continuous Electron Beam Accelerator Facility) recirculating linac represents the largest scale application of superconducting RF (SRF) technology to date. The accelerating structures in CEBAF are 169 pairs of 1.5 GHz SRF five-cell cavities-9 pairs in an injector and 80 pairs each in two linacs. Commissioning is now underway, with full energy beam expected in early 1995. All of the cavities have been assembled and have completed RF testing at 2.0 K in vertical dewars and in the accelerator. There was a significant reduction in performance in the accelerator. The difference in Q is ascribed to hydride precipitation enhanced by the slower cooldown in the accelerator.         Preparation method and RF behaviour of Nb/sub 3/Sn thin films obtained by bronze process    M.J. Durante, R. Musenich, R. Parodi, G. Gemme, P. Fabbricatore, B. Zhang, U. Gambardella, V. Boffa, C. Bottino and V. Buscaglia Summary: Aiming to application in RF devices, a method to obtain Nb/sub 3/Sn thin films, combining sputtering technique and bronze process, has been developed. A niobium film, 300-500 nm thick, is deposited by sputtering onto a 7 at.% tin bronze substratum. In order to allow the diffusion of tin into niobium and the formation of the A15 phase, the sample is maintained at about 700/spl deg/C during the deposition, and for several hours after the deposition. A Nb/sub 3/Sn film with very good adhesion on the substratum has been obtained. The RF behaviour of the film has been analyzed at about 10 GHz at temperature near Tc, using a host copper cavity having the top plate substituted with the bronze-Nb/sub 3/Sn sample. Both the quality factor and the frequency shift have been measured.         FENIX experimental results of large-scale CICC made of bronze-processed Nb/sub 3/Sn strands    S.S. Shen, B. Felker, J.M. Moller, J.M. Parker, T. Isono, Y. Yasukawa, F. Hosono and M. Nishi Summary: The Fusion Engineering International Experiments (FENIX) Test Facility has successfully completed the testing of a pair of Nb/sub 3/Sn cable-in-conduit conductors developed by the Japan Atomic Energy Research Institute. These conductors, made of bronze-processed strands, were designed to operate stably with 40-kA transport current at a magnetic field of 13 T. In addition to the measurements of major design parameters such as current-sharing temperature, FENIX provided several experiments specifically designed to provide results urgently needed by magnet designers. Performed experiments include measurements of ramp-rate limit, current-distribution, stability, and joint performance. This paper presents the design and results of these special experiments.         Improvement of I/sub c/ in Nb/sub 3/Sn conductors by reduction of axial prestrain    W. Specking and J.L. Duchateau Summary: Nb/sub 3/Sn conductors for large scale applications consisting of a high volume fraction of structural material which degrades I/sub c/ drastically because of the compressive prestrain on the Nb/sub 3/Sn filaments. This results from the higher thermal contraction of the structural components in comparison to that of Nb/sub 3/Sn during cooling from reaction to operation temperature. For example, in Nb/sub 3/Sn "Cable in Conduit" conductors using steel conduits I/sub c/ decreases by about 50% relative to the peak value at 12 T. Several alternatives for the reduction of the prestrain are possible leading to a remarkable improvement of I/sub c/: prestraining of the reacted conductor at room temperature; attaching the structural components onto the Nb/sub 3/Sn cable after reaction heat treatment of the cable; using reinforcing materials with lower thermal contraction coefficient comparable with that of Nb/sub 3/Sn.         Development of a prototype thin superconducting solenoid magnet for the SDC detector    A. Yamamoto, O. Araoka, Y. Doi, T. Haruyama, K. Kasami, N. Kimura, T. Kondo, Y. Kondo, Y. Makida, S. Suzuki, K. Tanaka, H. Yamaoka, R.W. Fast, C. Grozis, R. Kephart, Ang Lee, R.P. Stanek, A.M. Stefanik, R. Wands, C.A. Collins, M.E. Wilson, T. Hirano, Y. Hirata, T. Maeto, S. Mine, H. Mukai, I. Odajima, I. Watanabe, M. Ikeda, I. Inoue and T. Suzuki Summary: A prototype thin superconducting solenoid magnet has been developed to verify technical feasibility of an advanced thin superconducting solenoid magnet with a magnetic field of 2 T in a cylindrical volume of 3.4 m /spl phi//spl times/9 m and with a transparency of 1.2 radiation length (Xo). The magnet is required to have a stored energy/effective cold mass (E/M) ratio of 7.5 kJ/kg. The technical goal has been successfully achieved with realizing E/M=9.6 kJ/kg as a result of the prototype R&D. The prototype development and test results are presented.         The large superconducting solenoids for the g-2 muon storage ring    G. Bunce, J. Cullen, G. Danby, J. Jackson, L. Jia, R. Meier, W. Morse, C. Pai, I. Polk, A. Prodell, R. Shutt, L. Snydstrup, M.A. Green and A. Yamamoto Summary: The g-2 muon storage ring at Brookhaven National Laboratory consists of four large superconducting solenoids. The two outer solenoids, which are 15.1 meters in diameter, share a common cryostat. The two inner solenoids, which are 13.4 meters in diameter, are in separate cryostats. The two 24 turn inner solenoids are operated at an opposite polarity from the two 24 turn outer solenoids. This generates a dipole field between the inner and outer solenoids. The flux between the solenoids is returned through a C shaped iron return yoke that also shapes the dipole field. The integrated field around the 14 meter diameter storage ring must be good to about 1 part in one million over the 90 mm dia. circular cross section where the muons are stored, averaged over the azimuth. When the four solenoids carry their 5300 A design current, the field in the 18 centimeter gap between the poles is 1.45 T. When the solenoid operates at its design current 5.5 MJ is stored between the poles. The solenoids were wound on site at Brookhaven National Laboratory. The cryostats were built around the solenoid windings which are indirectly cooled using two-phase helium.         Field flattening in superconducting beam transport magnets    G.H. Morgan Summary: Dipoles in which the beam traverses the midplane well away from the magnet axis may benefit from flattening of the vertical field on the midplane. A procedure is described for doing so, making use of Chebyshev polynomials. In the case of the large aperture "DX" magnets located immediately on each side of the six intersection regions of the Relativistic Heavy Ion Collider (RHIC), a comparison is made of the field of coils optimized in this way and of coils optimized in the more common way by minimizing the leading coefficients of the Fourier expansion about the magnet axis. The comparison is of the integrated Fourier coefficients of the field expanded locally along the beam trajectory.         Passive persistent current correctors for accelerator magnets    H. Gurol, G.W. Albert and R. Simon Summary: Persistent currents in the superconducting material of conductors in superconducting particle accelerator magnets produce large nonuniformities in the magnetic field at low (injection) fields. The purpose of this paper is to discuss a simple, passive approach to reduce the multipole content of accelerator magnets at low magnetic fields. Calculations were performed to determine methods of reducing the b/sub 2/, b/sub 4/, and b/sub 6/ multipoles. Thin nickel strips are added at precise locations along the outer surface of the beam tube in the magnet. The length of the strips is about 1 meter. Magnetization of the nickel counters the multipoles caused by the persistent currents up to about 2 T. A sample beam tube was prepared with nickel strips and inserted into a prototype collider dipole magnet (CDM) cold mass. The magnet was tested warm at currents up to 30 amperes. Measurements of radial flux density were performed at a series of points along the inner surface of the beam tube to assess the effect of the nickel strips. The test results were compared with predicted values from a finite element model of the magnet. The corrector strips are found to correct the field nonuniformities, in qualitative agreement with calculated results.         Construction of prototype active shield dipole magnets for KEK B-Factory    N. Ohuchi, Y. Ajima, T.M. Kobayashi, K. Tsuchiya, T. Ogitsu, T. Haruyama and Y. Doi Summary: A special dipole magnet, which has the leak field less than 5 mT at r=200 mm with the dipole of 0.7 T, has been constructed as a candidate of the KEK B-Factory interaction region magnets. The magnet was energized to the design current of 3871 A without any quench. The multipole components in the magnet bore were measured and the results are consistent with the calculations.         Field measurements of superconducting bending magnets for compact storage ring    T. Matsuda, T. Takeuchi, S. Yamamoto, M. Morita, I. Kodera, T. Kawaguchi, T. Koujiro, S. Nakamura and T. Yamada Summary: We have constructed 180 degree superconducting bending magnets for compact electron storage rings and tests of magnetic field qualities of the magnets have been performed. Measured field qualities are; (1) high field homogeneity (normalized field errors are less than 1/spl times/10/sup -3/ over the electron beam aperture), (2) high field stability (the decay of the field is less than 0.1%/year) at persistent current mode of 3.5 T, (3) small gradient of coil axis (the averaged value is 0.5 mrad), and (4) small difference of the fields between two magnets (the difference is less than /spl plusmn/1/spl times/10/sup -3/). From the tests of field qualities, we confirm that the magnets have good performance for electron beam storage. An electron beam of 600 MeV can be stored.         Superconducting fast cycling magnets of the Nuclotron    A.M. Baldin, N.N. Agapov, A. Averichev, A.M. Donyagin, E.I. D'yachkov, H.G. Khodzhibagiyan, A.D. Kovalenko, L.G. Makarov, E.A. Matyushevsky and A.A. Smirnov Summary: The new superconducting heavy ion synchrotron-Nuclotron was put into operation at the Laboratory of High Energies. The maximum design energy is 6 GeV/u. There are 160 pulsed SC magnets with a "cold" iron yoke and a hollow superconductor winding in the ring. A magnetic field of 2 T is provided under a supply current of 6 kA. The magnets were tested under a cycle dB/dt=4 T/s, B=2 T, and a ramp rate f=1.0 Hz. A two-phase helium flow was chosen as a coolant. The Nuclotron "cold" mass is about 80 tons. The cryogenic supply system capacity is 4.8 kW at 4.5 K. The total running time of the Nuclotron reached 1100 hours after the last run in March 1994.         A final-focus magnet system for PEP-II    C.E. Taylor, S. Caspi and N. Saho Summary: A compact quadrupole magnet has been designed for the final-focus of the 3 GeV/spl times/9 GeV PEP II B-factory collider being built at SLAC. The magnet system must fit within the particle detector, has no iron, and consists of four nested separately controlled magnets: a two-layer 11.95 T/m quadrupole; a horizontal dipole; a vertical dipole; and a 1.5 T solenoid. The 1.1 m long magnet must produce a highly uniform quadrupole field in the 120 mm ID beam pipe. The cryostat is 140 mm ID (warm), 314 mm OD, and approximately 1.5 m long. The very compact cryogenic suspension system using Ti alloy plates is designed to withstand large forces due to interaction between the field of the detector solenoid and the four nested magnets. Cryogenic services and magnet leads are provided through a single flexible transfer line approximately 4 m long.         A fiber-optic strain measurement and quench localization system for use in superconducting accelerator dipole magnets    J.M. van Oort, R.M. Scanlan and H.H.J. ten Kate Summary: A novel fiber-optic measurement system for superconducting accelerator magnets is described. The principal component is an extrinsic Fabry-Perot interferometer to determine localized strain and stress in coil windings. The system can be used either as a sensitive relative strain measurement system or as an absolute strain detector. Combined, one can monitor the mechanical behaviour of the magnet system over time during construction, long time storage and operation. The sensing mechanism is described, together with various tests in laboratory environments. The test results of a multichannel test matrix to be incorporated first in the dummy coils and then in the final version of a 13 T Nb/sub 3/Sn accelerator dipole magnet are presented. Finally, the possible use of this system as a quench localization system is proposed.         2D coupled structural/magnetic analysis of SSC CQM    Xianrui Huang and G.A. Lehmann Summary: The deformation of a collider quadrupole magnet (CQM) coil under pre-compression, cool down and Lorentz forces may cause some significant changes in magnetic multipoles. The magnetic measurements of the CQM short model magnets at 4.2 K showed an average b/sub 5/ of -2.866 units compared to a numerical prediction of -0.162 units. Out of these -2.866 units, -1.5 units are due to a shim placed at the mid-plane to increase coil precompression. We also suspect that the permeability of the stainless steel collar may contribute some of the missing b/sub 5/. For example, a permeability of 1.004 for the collar adds -0.5 units of b/sub 5/. Including the collar, we are still missing -0.8 to -1.0 units. We believe that the mechanical deformation due to pre-compression of the coil is responsible for the remaining units. This study builds a 2D magneto-structural coupled model, calculates the magnetic multipoles under different loading conditions and establishes a correlation between multipole changes and coil pre-compression and Lorentz force stresses.         Superconducting 180 kA NbTi cable    A.D. Nikulin, B.V. Jakovlev, E.I. Plashkin, E.V. Nikulenkov, T.A. Morozova, G.K. Zelenskiy, L.V. Potanina, M.M. Potapenko, G.P. Vedernikov, V.Ya. Fil'kin, N.I. Salunin, I.N. Gubkin, V.I. Urakov, E.A. Oskolkov, G. Deis and N. Martovetsky Summary: The cable for the GEM detector superconducting magnet consists of 450 strands, which have the ratio of Cu:nonCu equal to 3.6:1. The design of the strand is a very important factor: arrangement of filaments, content of copper in the central and peripheral parts of the strand, and the thickness of Nb barrier. The quality of NbTi alloy and route of heat treatment of the strand strongly effect on the breakage of filaments. Optimal regimes of treatment the 0.73 mm strand allow to attain Ic higher than 420 A in magnetic field 2 T at 0.1 /spl mu/V/cm. The necessary equipment for production of the cable with the length of more than 1 km have been chosen, probed and adjusted.         Development of Nb/sub 3/Al multifilamentary superconductors    N. Ayai, Y. Yamada, A. Mikumo, K. Takahashi, K. Sato, N. Koizumi, M. Sugimoto, T. Ando, Y. Takahashi, M. Nishi and H. Tsuji Summary: Nb/sub 3/Al/Cu multifilamentary strands fabricated by the Jelly-roll process, and cable-in-conduit conductors have been developed for fusion magnets. The recent strand has achieved a high critical density of 800 A/mm/sup 2/ (12 T, 4.2 K) with a feasible heat treatment condition for large coils or conductors. The improved strands have were also confirmed to good bending and tensile strain tolerance. A cable-in-conduit Nb/sub 3/Al superconductor with 1152 strands was also developed. It has a titanium conduit and center tube, conforming to the current design for ITER magnets.         Development of 10-kA Nb/sub 3/Al coil    M. Sugimoto, T. Sasaki, M. Nishi, Y. Takahashi, T. Ando, H. Tsuji, Y. Yamada, N. Ayai, K. Takahashi, T. Fujioka, T. Hanai, S. Oukita and T. Horiya Summary: A 10-kA Nb/sub 3/Al coil was developed and tested to demonstrate a large current and a long length cable-in-conduit conductor which consisted of Nb/sub 3/Al wires. The fabrication of the 10-kA Nb/sub 3/Al coil was completed in June, 1993. The 10-kA coil has 124 mm-I.D., 408 mm-O.D., and 254 mm-height. The coil was designed 12 T of the maximum magnetic flux density at 10 kA of the coil current with 8 T of the back ground field. The 10 kA coil is wound by the cable-in-conduit conductor which consists of 108 Nb/sub 3/Al wires. The conductor is a 100 m length and the conduit material is titanium. The single Nb/sub 3/Al wire has 0.86 mm diameter, and is processed by Jelly-Roll method. The experiment of the coil was carried out on August, 1993. The coil was achieved 10 kA with the single charge operation and 10 T with the back ground field. The design and fabrication of the coil are reported. And the experimental results is also discussed.         Alternative strand material for the toroidal field coils of the ITER magnetic system: assessment of Nb/sub 3/Al    O. Cicchelli, L. Bottura, P. Gislon and M. Spadoni Summary: Designers of conductors for ITER TF coils selected Nb/sub 3/Sn as the strand material. As the influence of stress and strain on the superconducting property in Nb/sub 3/Al conductors is smaller than in Nb/sub 3/Sn conductors, Nb/sub 3/Al has become a potentially attractive candidate material. However, its industrial production has not yet been developed at the level of Nb/sub 3/Sn. Of interest is the evaluation of the use of cable-in-conduit-conductors for ITER TF coils. The assessment is carried out considering alternative jacket material (stainless steel), manufacturing approaches (winding of reacted conductors) and performance of the final conductor in the operating conditions of ITER TF coils.         Strand production and benchmark testing for the ITER model coils    N. Mitchell, P. Bruzzone, M. Spadoni, M. Nishi, A. Shikov and J. Minervini Summary: As part of the technology demonstration for the main features of the ITER Tokamak superconducting coils, two model coils, characteristic bore 2/spl divide/3 m, will be manufactured jointly by the four ITER partners. The coils will require a total of 26 tonnes of Nb/sub 3/Sn strand, supplied equally by each of the partners. The procurement of the strand is proceeding in stages, with performance and continuous quality demonstrated first on about 1t from each party underway since Sept. 93 and due for completion by Oct. 94. The strand uses both the bronze and internal tin routes, achieving jc(noncopper) in the range 550-700 A/mm/sup 2/ at 12 T and 4.2 K, with hysteresis losses from 200 to 600 mJ/cc(nonCu) for +/- 3 T cycle. Unit lengths >1.5 km are required with diameters about 0.8 mm. The status and parameters achieved in the production is reported. One of the first steps in confirming the strand quality has been to establish consistent testing procedures through a benchmark activity using strand exchange between all parties. The first block of testing was completed in May 94 and a second round is now underway. The results of the two rounds and the steps taken to standardise the testing are described.         Development and testing of 40-kA, 13-T Nb/sub 3/Sn cable-in-conduit conductors for a fusion reactor    T. Isono, Y. Yasukawa, F. Hosono, M. Nishi, H. Fujisaki, M. Sugimoto, K. Yoshida, Y. Takahashi, T. Ando, H. Tsuji, S. Shen, B. Felker, J. Parker Jr. and M. Chaplin Summary: The Japan Atomic Energy Research Institute (JAERI) has progressed development of a 40-kA, 13-T cable-in-conduit conductor for a central superconducting solenoid coil of a fusion reactor. Two types of developed full-scale conductors were tested under the US-Japan Collaboration Program at the Fusion ENgineering International eXperiment (FENIX) Test Facility in the Lawrence Livermore National Laboratory (LLNL) which has a pair of 13-T, 320-mm bore large split magnets and a more than 40-kA power supply. Each conductor consists of around 700 bronze processed (NbTi)3Sn strands and a titanium conduit. The superconducting performance tests such as current sharing temperature (Tcs) measurement test were carried out. Through a series of experiments, it was confirmed that the conductor satisfied their designed temperature margin of 2 K or more at their rated conditions. In this paper, the development of full-scale conductors is described and measured Tcs values are discussed.         Conduit distortion of the ITER CS conductor due to bending    P.A. Sanger, T.D. Hordubay and S.K. Singh Summary: In the high quality windings that are required in the ITER system, distortion of the cable in conduit conductors due to the winding process must be addressed and techniques developed to control and minimize these effects. To this end, a series of interviews were held with experts in the field of bending including manufacturers of bending tooling and equipment. Subsequently a test program was initiated to validate the ideas generated during the interview process by bending lengths of the 52.6 mm square CS empty conduit using the roll forming and compression bending approaches. Measurements of the distortion were made and both tooling and technique modifications were made. In the paper a summary of the techniques reviewed and the results of the experimental program are described.         Stability and safety estimates and tests of a superconducting bus-line for large-scale superconducting coils    T. Mito, S. Yamada, H. Chikaraishi, K. Takahata, N. Yanagi, A. Iwamoto, A. Nishimura, S. Tanahashi, O. Motojima, J. Yamamoto, T. Uede, H. Hiue, K. Ueda and I. Itoh Summary: We have been developing a flexible superconducting bus-line as a unit electrical feeder between large-scale superconducting coils and their power supplies away from the coils. The designed superconducting bus-line consists of a pair of +/- aluminum stabilized NbTi/Cu compacted strand cables and a coaxial four-channel transfer line. A full-scale model of the SC bus-line (20 m long) has been constructed and tested successfully up to 40 kA without a quench under the short-circuit condition. Stability tests were also done by inducing a forced quench with heaters. A minimum propagation current larger than 32.5 kA was confirmed. Thus, the bus-line was cryogenically stabilized at the rated current of 30 kA. We have examined the test results and evaluated the stability and safety margins of this bus-line. The design criteria for a superconducting bus-line are also shown for large-scale superconducting coils with operating current as a parameter.         3-D stress analysis of the TPX toroidal field coil support structure    R.L. Myatt Summary: A 3-D, coupled, electromagnetic and stress analysis of the Tokamak Physics Experiment (TPX) toroidal field (TF) coil support structure is presented. The analysis makes use of one-eighth toroidal symmetry to simulate the magnetic field and structural characteristics of the superconducting TF and poloidal field (PF) coil systems. Notable extensions to past work include the addition of the PF coil set and the coupled electromagnetic and structural solution technique. In this analysis, the PF coils are included in the magnetic field calculations and attached to the TF cell structure to simulate the appropriate structural interaction. The effects of attaching the PF ring coils directly to the TF coil cases, with no provisions for free radial relative motion, are evaluated and discussed. The effects of various PF coil operation points are also discussed. Stress results are compared to the TPX structural design criteria to evaluate the general adequacy of the overall design.         Thermal analysis of the TPX TF coil case for eddy-current and neutron heating    R.L. Myatt, A.L. Radovinsky and R.D. Pillsbury Jr. Summary: A finite element, thermal analysis of the Tokamak Physics eXperiment's (TPX) toroidal field (TF) coil case is presented. The analysis models the 316LN coil case as a 3-D shell with imposed thermal loads dominated by neutron and eddy current heating. Heat sinks which simulate the flow of supercritical helium in the coil case cooling system and adjacent conductor conduits are used to extract the steady-state heat load. The model is used to estimate the heat leak rate into the winding pack as input for heat removal and conductor temperature margin calculations. The proposed cooling scheme flows 5 K helium at 5 atmospheres to the TF coil winding packs. The effluent is directed into the case cooling channels. Results indicate that the case cooling system and ground wrap insulation are effective means of thermally isolating the superconductor from the heat deposited in the coil case; 92% of the 8.07 kW deposited in the cell cases by eddy currents and neutrons are extracted by the helium flowing in the case cooling channels while only 0.65 kW are transmitted into the adjacent conductors of the winding packs.         Structural characteristics of the TPX CICC-based TF coil winding pack    R.L. Myatt Summary: A detailed finite element analysis of the Tokamak Physics eXperiment's (TPX) superconducting toroidal field (TF) cable-in-conduit conductor (CICC) is presented. The analysis focuses on the equatorial plane of the inboard leg, where electromagnetic forces are the highest, and the stress field of the 84-turn conductor array can be well characterized by a 2-D model. The 40,000 element, coupled, electromagnetic and structural model provides a convenient means of solving for the magnetic field and stress distribution in a single analysis. Particular attention is given to understanding the structural behavior of the conduit and insulation in this geometry, as the integrity of these element is critical to the life of the coil system. In addition, stress data is processed to evaluate the conductor design relative to the TPX structural design criteria.         Characteristics of an "overload component" for low-Tc superconducting winding systems    S. Yoshida, S.W. Biggins, K.V. Ravikumar and T.H.K. Frederking Summary: Small Nb/Ti-Cu prototype superconducting coils have been wound using LBL-supplied wire, which has been normally applied to Rutherford cabled dipoles. The studies are being conducted in the context of planning versions of toroidal winding systems for an eventual conversion of the normal windings of an intermediate size system, such as the 1994 UCLA Tokamak, to superconducting coils. At this time initial data have been collected and-a novel quench inducing device (QID) has been tested. The magnet field intensities generated by the prototype magnet were measured and compared with the design values. Quench propagation has been investigated including stability behavior of the magnet. At low currents, a quenched domain close to the inner winding layer was found to be stationary, not propagating into the magnet during runs which did not encounter a severe quench.         Comparison between superconducting and conventional power transformers considering auxiliary facilities    H. Yamaguchi, Y. Sato and T. Kataoka Summary: Due to the remarkable progress of AC superconducting wires, superconducting power transformers, which have the advantages of the reduction of size, weight and loss, are being investigated actively. However, considering the auxiliary facilities such as an outer cryogenic system, these advantages of the superconducting transformer over the conventional transformer are unclear. Thus, in this paper, a comparison of the size, weight and loss of superconducting transformers including auxiliary facilities with those of conventional transformers having the same output volt-ampere capacity is made. From the results of the comparison, the advantages of superconducting transformers are clarified.         Characteristics of a 40 kVA three phase superconducting transformer and its parallel operation with a conventional transformer    T. Ise, Y. Marutani, Y. Murakami, E. Yoneda and R. Sugawara Summary: A 40 kVA three phase superconducting transformer has been developed and tested. From the test results, excellent voltage regulation of 0.3% with a pure resistive load was obtained. For application in a power system, parallel operation with a conventional power transformer using copper windings has been carried out. Although a superconducting transformer cannot continue to operate in case of quenching, the proposed parallel system can overcome the drawback and give an additional fault current limiting function.         Development of the prospective power transmission model system integrated under superconducting environment-PROMISE    Y.J. Tang, T. Kato, N. Hayakawa, Y. Yokomizu, T. Matsumura, H. Okubo, Y. Kito, K. Miyake, T. Kumano, W. Satoh and K. Satoh Summary: A "prospective power transmission model system integrated under superconducting environment", abbreviated to PROMISE, has been constructed to verify the technical possibility of superconducting power transmission for the next generation. PROMISE is composed of a superconducting transformer, a superconducting fault current limiter and superconducting power cable of length 5 m. These three superconducting apparatus are enclosed together in a long scale cryostat to be kept at the liquid helium temperature of 4.2 K. The major insulation is provided by liquid helium. PROMISE withstands an AC voltage of 6 kV for 2 minutes with quite low partial discharge. A voltage-current synthetic test has proved that PROMISE has a transmission capability of 6,000 V-1,000 kVA. The fault current limiter actually limits overcurrent and prevents the other apparatus from quenching. Quench current level coordination is actually realized in PROMISE.         A feasibility study on a world-wide-scale superconducting power transmission system    T. Ishigohka Summary: The author has conceptually designed two types of superconducting DC power cable (SCDCPC) using high temperature superconductors. One is cooled by liquid hydrogen, and the other is cooled by liquid nitrogen. The former has a capacity of 50 GW, and the latter has a capacity of 20 GW, So as to reduce losses as low as possible, the DC system has been selected. The rated voltage for both systems is /spl plusmn/250 kV. Because of the merit of DC operation, these cables generate neither conductor loss nor dielectric loss induced by AC operation, and so have extremely high efficiency. In the case of 10,000 km transmission, Including the refrigeration power, the total loss is lower than 1%. A concept of a world-wide superconducting power transmission system using SCDCPCs is presented.         Performance summary of a 4,000 a high temperature superconducting cable conductor prototype    J.J. Gannon Jr., M.J. Minot, D. Buczek, G. Vellego and P. Metra Summary: Multifilamentary superconducting Bi-2223 tapes made with a powder-in-tube process have been used to assemble multistrand, multilayer cable conductor prototypes. The electrical performance of these conductors has been evaluated at 77 K in self-field with DC and AC transport currents. Results show that these conductor prototypes, carrying up to 4,200 A DC, approach the 2,000 A AC operation threshold required for the commercial application of HTS power transmission cables. Combined with recent improvements in tape mechanical performance, stability, and long-length manufacturability, these results show the potential for use of HTS tapes in power transmission cables.         Characteristics of heating in a superconducting coil mechanically vibrated    E. Suzuki and M. Ogata Summary: The superconducting magnet on a Maglev vehicle vibrates and heats inside under the influence of various disturbances in running. The authors have investigated the characteristics of heating in a superconducting coil mechanically vibrated under a purely mechanical actuating force without any electric factors. The amount and features of this heat generation are discussed in this paper.         A cryogen-free superconducting magnet for Maglev applications: design and test results    K.G. Herd, E.T. Laskaris, P.S. Thompson and S. Kalsi Summary: A novel cryogen-free superconducting magnet for use in levitating and propelling Maglev vehicles has been developed and tested. The magnet is conduction-cooled by a two-stage CTI Cryodyne-1020 Gifford-McMahon cryogenic refrigerator. YBCO high-Tc superconducting current leads are incorporated in order to minimize the heat leak to the magnet. A low eddy-current cryostat has been fabricated using fiberglass-reinforced epoxy structures with subdivided stainless steel permeation barriers. The magnet has been cooled to approximately 10 K and ramped to the design current of 100 amps DC. The magnet has also been operated with a 20 Hz, +/-15 amp sinusoidal excitation. Test results for the thermal and magnetic performance of the magnet are presented.         Iron-core superconducting magnet design and test results for Maglev application    S. Kalsi, M. Proise, T. Schultheiss, B. Dawkins and K. Herd Summary: Design and test results are presented for a superconducting electromagnet for levitating and propelling Maglev vehicles at high velocities. A U-shaped iron core carries a superconducting magnet around its back leg and a normal control coil around each leg of the U-core. The open side of the U-core is bridged by an iron rail through a large airgap between the poles of the U-core and the iron rail. The superconducting magnet is nominally designed to operate in a steady-state DC mode with current variations limited to rates less than 1 Hz. Faster flux variations due to gap changes are accommodated by current changes in the normal control coils. A feedback controller using the airgap and acceleration inputs controls current variations in the superconducting coil. Grumman has designed, fabricated and tested such an electromagnet. This test magnet is 2/3 of the full-size magnet that Grumman specified in their 1992 Concept Definition Study for the National Maglev Initiative. The purpose of these tests is to demonstrate the feasibility of operating and controlling a superconducting electromagnet in the specified environment. This paper discusses static magnet levitation characteristics as functions of airgap length and superconducting magnet excitation. Good correlation is observed between the calculated and measured performance.         Demonstration of two synchronous motors using high temperature superconducting field coils    C.H. Joshi, C.B. Prum, R.F. Schiferl and D.I. Driscoll Summary: The design, construction and testing of two synchronous motors, having output powers of 1.5 kW and 3.7 kW respectively, is described. Both motors have a salient pole field structure excited by high-temperature superconductor (HTS) coils. The first motor (1.5 kW) is a vertical axis, two-pole machine operating at 3600 rpm with a stationary field structure and a rotating armature whereas the second motor (3.7 kW) has a more conventional rotating field structure with four salient poles operating at 1800 rpm. The racetrack-shaped coils are made with flexible multifilamentary BSCCO conductor and operate at liquid nitrogen temperature and remained superconducting under all operating conditions. Each HTS coil contains approximately 170 m of conductor. The coils used in these motors have experienced over 40 thermal cycles with no degradation in performance. These demonstration motors represent a significant advancement in the application of HTS to electrical rotating machinery.         A superconducting linear motor drive for a positive displacement bellows pump for use in the g-2 cryogenics system    M.A. Green Summary: Forced two-phase cooling of indirectly cooled superconducting magnets requires circulation of liquid helium through the magnet cooling channel. A bellows helium pump is one possible way of providing helium flow to a magnet cooling system. Since the bellows type of helium pump is immersed in liquid helium, a superconducting linear motor drive appears to be an attractive option. This report describes a linear motor drive that employs oriented permanent magnet materials such as samarium-cobalt as the stator magnet system and a superconducting loudspeaker voice coil type of drive as the armature of the linear motor. This report examines drive motor requirements for a helium pump.         Development of prototype superconducting linear induction motor for steel making processes    O. Tsukamoto, N. Amemiya, K. Yamagishi, S. Sato, K. Sato, T. Takao and H. Shimizu Summary: The authors describe how they are developing technologies of a superconducting linear induction motor (SLIM) for steel making process applications. They have developed and tested a prototype SLIM and this paper presents configurations and test results of the SLIM.         Development of a double stranded cable superconductor for 70 MW class superconducting generator with quick response type    H. Takigami, K. Nakanishi, H. Nakamura, S. Meguro, S. Akita and S. Ohshima Summary: We have been developing a 70 MW class model generator aiming at a 200 MW class pilot machine. The superconductor developed for field winding of a generator has a configuration of double stranded cable, composed of NbTi, Cu and CuNi. The strand is insulated by formvar and seven strands make a 1st stage cable. Eleven 1st stage cables make a 2nd stage cable, and are compacted to rectangular cross section. The inter-strand resistance and AC loss of superconductors are measured under the conditions of compressive mechanical force up to 19.6 MPa to simulate the centrifugal force of the generator rotor winding. From those results, we consider the relation between inter-strand resistance and inter-strand coupling loss. Based on those results, we are designing the superconductors for the 70 MW class model generator with quick response, taking the insulation of the strand into account.         AC losses in multifilamentary superconductors carrying transport current and exposed to external magnetic field-analysis of temporal evolution of current distribution    N. Amemiya, N. Banno, K. Inaho and O. Tsukamoto Summary: The temporal evolutions of current in multifilamentary superconductors were calculated numerically, while they were carrying the transport current and exposed to the spatially-distributed external magnetic field. Multifilamentary superconductors were represented with an electrical circuit model assuming the axisymmetric current distribution. The current distribution is substantially influenced by the axial distribution of the longitudinal magnetic field. AC losses were calculated from the temporal evolutions of the current distribution. Influence of the transport current and the longitudinal component of the external magnetic field distributed spatially on the losses was studied. The additional losses due to the transport current and the longitudinal magnetic field are not negligible as compared to the losses due to the transverse magnetic field.         Application of 50 Hz superconductors close to self field conditions    P. Estop, C. Cottevieille, S. Poullain, J.P. Tavergnier, T. Verhaege, A. Lacaze, Y. Laumond, S. Le Naour, A. Ansart and P. Manuel Summary: Applications of 50 Hz superconductors like the transformer and the fault current limiter correspond to relatively low magnetic fields, so that AC losses and stability are mainly governed by the conductor self field. AC loss calculations as they are performed in most cases for superconductors, are based on the Bean critical state model which states that everywhere in a superconductor, the current density has a modulus equal to the critical current density J/sub c/. This model is applicable when the superconducting transition E(J) is very sharp, but sizeable discrepancies appear for 50 Hz superconductors, as they present a relatively smooth superconducting transition. AC loss calculations have been developed using the Maxwell equations combined with the actual E(J) relationship. The heat generation in the conductor is then used as an input for a numerical calculation of the temperature distribution through the superconductor. The stability limits are directly derived from the thermal model.         First results of a parametric study on coupling loss in subsize NET/ITER Nb/sub 3/Sn cabled specimen    A. Nijhuis, H.H.J. ten Kate, P. Bruzzone and L. Bottura Summary: The cable in conduit conductor for the ITER coils is required to function under pulse conditions and fields up to 13 T. A parametric study, restricted to a limited variation of the reference cable lay out, is necessary to identify the quantitative impact of manufacturing parameters on the coupling loss and to find out more precisely the value of the coupling loss time constant to be used in the AC loss computation. Here we present the first results of the AC coupling loss measurements on jacketed sub size conductors with variations in type of cabling, cabling stage, twist pitch and void fraction. The AC loss is determined mainly by the calorimetric way but partly also using a magnetometer. A sinusoidal AC field amplitude of 15-400 mT, superposed on a DC background field of B/sub dc/=0, 1 or 1.5 T, is applied to determine the coupling loss time constants for different specimens. The results up to now show large coupling current time constants especially for braided cables, for which n./spl tau/ can reach more than 1000 ms. For twisted cables with 81 strands n./spl tau/ values up to 300 ms are attained.         DC resistance and eddy current losses in the ITER conductor joint    R.L. Myatt and R.D. Pillsbury Jr. Summary: The central solenoid (CS) and the toroidal field (TF) coils of the International Thermonuclear Experimental Reactor (ITER) are wound from superconducting (SC) Nb/sub 3/Sn Cable-in-Conduit-Conductor (CICC). Electrical joints are an important aspect of the coil design, since local heating from resistive losses can drive the superconductor into a less stable regime and possibly initiate a quench. A good joint design will satisfy the broadest requirement which is to minimize the power dissipation during normal coil operations. This can be achieved by satisfying two, more specific, and in some ways, conflicting requirements: (1) to provide a low DC resistance, and (2) to minimize the effects of Joule heating from eddy currents induced by transient magnetic fields. This paper presents a finite element analysis of the latest conductor joint concept and evaluates its electromagnetic characteristics with respect to these two requirements. The analysis extends the usual practice of representing the presence of superconductors with surface conditions by explicitly modeling the last stage of the twisted cable. Although certain modeling approximations limit the accuracy of the results, some valuable insights are gained, such as which approximations cannot be made, and the effects of various design details on the DC joint resistance and Joule heating.         Fabrication and component testing results for a Nb/sub 3/Sn dipole magnet    D. Dell'Orco, R.M. Scanlan, C.E. Taylor, A. Lietzke, S. Caspi, J.M. van Oort and A.D. McInturff Summary: At present, the maximum field achieved in accelerator R&D dipoles is slightly over 10 T, with NbTi conductor at 1.8 K. Although Nb/sub 3/Sn has the potential to achieve much higher fields, none of the previous dipoles constructed from Nb/sub 3/Sn have broken the 10 T barrier. We report here on the construction of a dipole with high current density Nb/sub 3/Sn with a predicted short sample limit of 13 T. A wind and react technique, followed by epoxy impregnation of the fiberglass insulated coils, was used. The problems identified with the use of Nb/sub 3/Sn in earlier dipole magnets were investigated in a series of supplemental tests. This includes measurement of the degradation of Jc with transverse strain, cabling degradation, joint resistance measurements, and epoxy strength tests. In addition, coil assembly techniques were developed to ensure that adequate prestress could be applied without damaging the reacted Nb/sub 3/Sn cable. We report here the results of these tests and the construction status of this 50 mm bore dipole.         Design and fabrication of end spacers for a 13 T Nb/sub 3/Sn dipole magnet    S. Caspi, D. Dell'Orco, W.B. Ghiorso and A. Wandesforde Summary: A 13 Tesla R&D dipole magnet is being constructed using Nb/sub 3/Sn superconducting cable. The four-layer "cosine-theta" magnet uses a wide cable (/spl sim/15 mm) that will undergo a 650 C reaction after each layer is wound. About 75 bronze spacers at the magnet "ends" separate the winding blocks in such a way that the stored strain energy in the cable is minimized and the integrated field harmonics are reduced. Wax prototypes of the designed spacers were made on a 5-axis milling machine. This method of rapid prototyping required no tooling and enabled us to produce a large number of different end spacers that can be physically inspected and repeatedly modified before final prototypes are made. Spacers were originally machined from wax billets which were later cast in bronze.         Design of a 16 T Nb/sub 3/Sn twin bore accelerator dipole with a window-frame conductor layout    J.M. van Oort and R.M. Scanlan Summary: A simplified design study of a 16 T Nb/sub 3/Sn twin bore accelerator dipole magnet is presented. The philosophy behind the study is to design a high field magnet with a coil structure optimized for a reasonable Lorentz-load and ease of construction. The coils are of the rectangular window-frame type with modular flat pancake windings, thus eliminating the need for complex coil return ends. The magnetic and structural design is presented and a comparison is made with existing cell layouts for high field magnets.         Quench antenna and fast-motion investigations during training of a 7 T dipole    A.F. Lietzke, R. Benjegerdes, P. Bish, J. Krzywinski, R. Scanlan, R. Schmidt and C.E. Taylor Summary: Equipment was installed to detect fast conductor motion and quench propagation in a 1 meter long superconducting dipole magnet. (1) The fast-motion antenna, centered within the bore of the magnet, used three long dipole coils, mounted end-to-end to span the magnet length. Coil signals were nulled against a neighbor to produce low-ripple signals that were sensitive to local flux changes. A low microphonic signal was used as an event trigger. (2) Nulling improvements were made for the magnet's coil-imbalance signals for improved cross-correlation information. (3) A quench-propagation antenna was installed to observe current redistribution during quench propagation. It consisted of quadrupole/sextupole coil sets distributed at three axial locations within the bore of the magnet. Signals were interpreted in terms of the radius, angle, orientation, and rate of change of an equivalent dipole. The magnet was cooled to 1.8 K to maximize the number of events. Twenty-four fast-motion events occurred before the first quench. The signals were correlated with the magnet-coil imbalance signals. The quench-propagation antenna was installed for all subsequent quenches. Ramp-rate triggered quenches produced adequate signals for analysis, but pole-turn quenches yielded such small signals that angular localization of a quench was not precise.         Development of twin aperture dipole magnets for the Large Hadron Collider    A. Yamamoto, T. Shintomi, N. Higashi, H. Hirabayashi, H. Kawamata, Naihao Song, A. Terashima, H. Yamaoka, S. Kawabata, G. Brianti, J. Buckley, D. Leroy, R. Perin, A. Siemko, L. Walckiers, M. Hirano, T. Origasa, K. Makishima, I. Inoue, M. Ikeda, S. Meguro and M. Kondo Summary: A twin aperture dipole magnet has been developed with a feature of symmetric, separate coil/collar design in a R&D cooperation between CERN and KEK towards the LHC (Large Hadron Collider) project. The magnet reached 8.1 T at 4.2 K and 9.6 T at 1.8 K in the training test. Development of the magnet and test results are discussed. Design study of a new 56 mm /spl phi/ twin aperture dipole is also discussed.         Ramp rate induced quenches in the one-metre dipole model magnets for the CERN LHC    A.P. Verweij, H.H.J. ten Kate, D. Leroy, L. Oberli and A. Siemko Summary: During the investigation of 1 m model dipoles for the Large Hadron Collider (LHC) a considerable number of quenches are performed at high ramp rate. In this paper the results are presented of these quenches which are made both at 1.7-2.1 K and at 4.3 K for ramp rates varying between 10 As/sup -1/ and 300 As/sup -1/. The quench current is strongly affected by the inter-strand coupling currents and the heat due to these currents. Furthermore, the influence of a current precycle is considered which can result in a significant increase of the quench current (at the same ramp rate). It is shown that this increase can be attributed to the presence of so called "super coupling currents" which strongly influence the current distribution among the strands, exhibiting characteristic time in the order of a few hundred to a few thousand seconds. Generally, the origin of the ramp rate induced quenches is close to the midplane of the inner coil of the magnet, where the field perpendicular to the wide side of the cable is maximum.         Dynamic magnetic measurements of superconducting magnets for the LHC    J. Buckley, D. Richter, L. Walckiers, R. Wolf and A. Verweij Summary: Several superconducting dipole magnets were manufactured in industry or at CERN as model magnets for the future Large hadron Collider (LHC) particle accelerator. Results of the measurements of the field quality is given for current variations in the range of those expected for the accelerator operation. We present measurements of the field errors resulting from persistent currents in the superconducting filaments, eddy currents flowing in and between the strands of the superconducting cable, and current differences between the strands of the cable.         Quench location in the superconducting model magnets for the LHC by means of pick-up coils    A. Siemko, J. Billan, G. Gerin, D. Leroy, L. Walckiers and R. Wolf Summary: High field superconducting dipole magnets were manufactured in industry or at CERN as model magnets for the future Large Hadron Collider (LHC) particle accelerator and tested in superfluid helium. The pick-up coil method is now in use to precisely locate the origin of training quenches and to monitor the propagation of the transition. The improvements made on this diagnostic method is reviewed. This experience allows the location of the onset of the quenches both axially and in the cross section of the winding even for magnets equipped with a minimum of voltage taps on the winding. The location of training quenches are now understood to be related to the structure of the superconducting coil.         Superconducting beamline elements for the NSCL spectrograph    A.F. Zeller, J.C. DeKamp, C. Magsig, J. Wagner and D. Pendell Summary: The superconducting beamline elements for a magnetic spectrometer at the National Superconducting Cyclotron Laboratory are being constructed. There are four dipoles, which produce a peak field of 1.7 T in a 7 cm gap, and fifteen quadrupoles, which have peak gradients of 25 T/m in a 20 cm diameter bore. A quadrupole has been tested to higher than the required current. All of the devices are being assembled into their cryostats.         Induced axial oscillations in superconducting dipole windings    W.B. Sampson and A.K. Ghosh Summary: When superconducting accelerator magnets wound from a multi-stranded conductor are energized, a periodic variation appears in the magnetic field along the axis. This oscillation is present in all components of the field and has a period that is equal to the transposition pitch of the superconducting cable. Such axial variations have been observed even in windings which are not carrying any transport current. A magnetic field was applied to a portion of a dipole winding using a second magnet. Axial oscillations were induced along the total length of the windings including the portion not in the applied field. The amplitude of these oscillations varied with the amount of inert winding inside the energizing magnet and with the angle of the applied field. These field variations could be completely eliminated in the external portion of the coil by heating a small section of the winding above the transition temperature.         Anisotropic high temperature superconductors as variable resistors and switches    H.J. Boenig, M.A. Daugherty, S. Fleshler, M.P. Maley, F.M. Mueller, F.C. Prenger and J.Y. Coulter Summary: Several anisotropic high temperature superconductors show critical current densities which are strongly dependent on the direction of an applied external magnetic field. The resistance of a sample can change by several orders of magnitude by applying a magnetic field. The potential for using the field dependent variable resistor or switch for applications in power systems is evaluated. Test results with small samples are presented, The requirements for large scale applications are outlined. The magnetic field triggering requirement, the frequency response of the device, use in 60 Hz AC circuits and heat transfer considerations are investigated. Several application examples are discussed. Use of the variable resistor as a fault current limiter, as a switching element in rectifier circuitry and as an improved dump resistor for a superconducting magnet is presented.         High-Tc superconducting inductive current limiter for 1 kV/25A performance    V. Meerovich, V. Sokolovsky, G. Jung and S. Goren Summary: The results of investigations of an inductive current limiting device prototype based on superconducting to normal state transition in 0.2 m o/d. BSCCO rings are discussed. Thermal processes in the ring were found to have an important influence on transient response characteristics of the limiter. In a marked difference to small scale devices, the quenching process in a medium scale current limiter is accompanied by an intense heating of the HTSC ring. Because of high losses and large thermal inertia, the superconducting ring remains in the normal state during entire limitation time and at least a few AC cycles pass before the superconducting state in the rings is resumed after a fault occurrence.         Short circuit test performance of inductive high T/sub c/ superconducting fault current limiters    D.W.A. Willen and J.R. Cave Summary: The current limiting performance of inductive fault current limiters based on Bi-2212 high temperature superconducting tubes has been evaluated. Fault current limitation is due to the nonlinear impedance of this device when the induced current in the superconducting Bi-2212 tubes exceeds the critical current. A power load in a test circuit is first operated in nominal power conditions (<10 kVA). A fault condition is then provoked by short circuiting the load. The limiter's current and voltage characteristics are recorded prior to and during the fault. Fault currents are limited to about 5-8 times the nominal current and limitation always occurs in the first cycle. Using an approximate transformer analysis with a shorted single turn secondary, the current in the superconductor and its effective resistance are obtained. The superconductor's effective resistivity is of the order of 10 /spl mu//spl Omega/cm at the onset of a fault and increases gradually as the fault progresses. Results for the evolution of the limiting impedance with time as the nominal voltage of the circuit is increased are presented. The materials requirements for this type of fault current limiter are discussed.         Preparation of high T/sub c/ superconducting coils for consideration of their use in a prototype fault current limiter    J.X. Jin, S.X. Dou, H.K. Liu and C. Grantham Summary: High T/sub c/ superconducting coils, made using Ag clad (Bi,Pb)SrCaCuO-2223 wires, have been used for building a small prototype of an electrical transmission system fault current limiter. The techniques for fabricating high T/sub c/ superconducting coils with the Bi-2223 Ag clad long wire are described, which include transferring the long wire to coils and wire-joining techniques to enhance total current ampere-turns of such coils. Testing with these coils includes the magnetic field dependence of its critical current I/sub c/, the mechanical bending property and cracks on the superconductor. The prototype based on the principle of a magnetic core saturable reactor is studied. The results from the superconducting coils and the prototype are helpful for evaluating the application of the high T/sub c/ superconductors in the electrical power system.         Experimental results on an hybrid superconducting current limiter    P. Tixador Summary: The superconducting current limiter, a device without classical equivalent, appears to be one of the most promising and innovative applied superconducting devices for electric power systems. Its operation is based on the ultra-fast and natural transition of a superconducting coil when the current oversteps a predetermined threshold value. The authors propose a hybrid device consisting of a resistive series transformer and superconducting coils. The superconducting coils trigger the limitation. The latter is ensured by the primary self inductance of the transformer. This design allows the reduction of the current through the superconducting cable, the volume of superconductor and the cryogenic losses under normal operation. These advantages are brought about by a transformer whose magnetic coupling between the windings changes accordingly to the mode of operation. To study this device experimentally, a 150 V-50 A model has been developed. This model has been exposed to a number of tests under normal and fault operations. The results have demonstrated the satisfactory performance of this hybrid device, at least at a reduced scale. With a view to an industrial device, a 63 kV-1250 A system has been theoretically designed.         Tests of 100 kW High-T/sub c/ superconducting fault current limiter    W. Paul, T. Baumann, J. Rhyner and F. Platter Summary: An inductive superconducting fault current limiter has been built and tested. It mainly consists of a copper coil, a superconducting tube, and an iron core which are concentrically arranged. The device is essentially a transformer with the secondary winding being the tube. The tube has diameter of 20 cm, a height of 35 cm, and is made of Bi2212 ceramic, fabricated by partial melting. The ceramic has the voltage current characteristic V-I/sup /spl alpha// with /spl alpha//spl ap/5. The critical current density defined by the 1 /spl mu/V/em criterion is about 1400 A/cm/sup 2/. Depending on the number of turns of the coil, the nominal current of the device was between 130 A and 250 A. In short circuit tests in a 480 V circuit, the prospective fault current of 8 kA was limited to about 5 times the nominal current. The test results are in good agreement with detailed simulations of both the normal operation (e.g. impedance, AC-losses) and the behaviour under fault conditions (i.e. evolution of the current).         Investigations of HV and EHV superconducting fault current limiters    T. Verhaege, C. Cottevieille, P. Estop, P.G. Therond, P. Thomas, Y. Laumond, M. Bekhaled, P. Bonnet and V.D. Pham Summary: In close cooperation, GEC Alsthom, Alcatel Alsthom Recherche and Electricite De France are investigating the technical feasibility and the economical impact of low T/sub c/ superconducting fault current limiters, intended for the French HV and EHV electrical grids. The program includes the complete design of a 63 kV/1.25 kA/5 kA/spl circ/ version, experienced on current and voltage models. Extensions to the HV prototype demonstration, and to the EHV fault current limiters, are also discussed in this paper.         A magnetic shielding type superconducting fault current limiter using a Bi2212 thick film cylinder    M. Ichikawa and M. Okazaki Summary: The application of a superconductor to a fault current limiter in a power system has been researched. The authors developed a magnetic shielding type superconducting fault current limiter using a Bi2212 thick film cylinder. This limiter consists of a primary winding on a superconducting cylinder for generating an AC magnetic field, the cylinder for shielding the field, an iron core for magnetic members and a control ring for controlling fault currents. When a fault occurs, the superconductive cylinder quenches and a magnetic circuit is formed inside the cylinder. As a result, the limiter has a high impedance to limit the fault current. The present study shows the limiting and recovery characteristics of the fault current limiter.         Current limiter based on melt processed YBCO bulk superconductors    J. Acero, L. Garcia-Tabares, M. Bajko, J. Calero, X. Granados, X. Obradors and S. Pinol Summary: One of the first applications of YBCO bulk superconductors developed in Spain within the framework of the MIDAS programme was the design and construction of a small inductive fault current limiter. This paper describes the whole process of design and manufacturing of the limiter, starting from the synthesis of the bulk superconductor to achieve a melt textured ring. Transport properties of this material are also described and measured. The second part of the paper describes the current limiter, starting from basic equations and the equivalent circuit which considers the device as a transformer, providing a useful tool for the design and simulation. After a description of the limiter and its main parameters, simulation results are compared to experimental measurements.         Application of superconducting shields in current-limiting and special-purpose transformers    Yu.A. Bashkirov, I.V. Yakimets, L.S. Fleishman and V.G. Narovlyanskii Summary: The principles of operation and the design of power transformers based on superconducting shields have been considered. The laboratory prototypes of fault current-limiting and special-purpose (arc welding/furnace) transformers have been tested. The application of both low-T/sub c/ and high-T/sub c/ superconducting shields has been studied.         Comparison of superconducting fault limiter concepts in electric utility applications    L. Salasoo, A.F. Imece, R.W. Delmerico and R.D. Wyatt Summary: A comparison or superconducting fault current limiter concepts is made for a specific transmission voltage, current and limiting level. Conceptual designs are developed and trade-offs are discussed together with electromagnetic transients program modeling results.         Aluminium stabilised superconducting cable development for high energy physics detector magnets    I.L. Horvath Summary: Under the leadership of the Swiss Federal Institute of Technology (ETHZ) an international ad hoc collaboration for conducting cables developed an aluminium stabilised superconducting cable for future detector magnets. With the financial support of the Swiss government, this R&D work was carried out for the European Organisation for Nuclear Research (CERN). In this report the manufacturing process is described and results of the quality control measurements are summarised. These tests showed that the industrial manufacturing of an aluminium stabilised superconducting cable is feasible.         Micromachined millimeter-wave SIS-mixers    G. de Lange, B.R. Jacobson and Qing Hu Summary: Micromachined SIS-mixers for 90-115 GHz and for 180-230 GHz have been fabricated and tested. A micromachined SIS-mixer consists of an antenna-coupled superconducting tunnel junction fabricated on a thin SiN membrane which is placed inside a pyramidal horn structure. The horn is formed by anisotropic KOH-etching of [100] Si along the (111) crystal planes. The high accuracy of the etching and the ease of whole-wafer fabrication make this type of SIS mixers attractive for applications both at high frequencies and in imaging arrays. Experimental results show that high-quality tunnel junctions can be reliably fabricated on thin SiN membranes. Experiments also show that the junctions are adequately cooled on the membrane and that sufficient LO-power can be coupled.         Effective parameters j/spl tilde//sub c/ and /spl lambda//spl tilde/J at commensurate fields in large Josephson junctions with periodic columnar defects    M.A. Itzler and M. Tinkham Summary: We have studied flux pinning effects in large Josephson junctions with lithographically patterned periodic columnar defects. At commensurate fields of an integral number of fluxons per defect, the junction behavior is analogous to that found at zero field and can be understood in terms of a field-dependent effective critical current density j/spl tilde//sub c/ which is smaller than the microscopic value j/sub c/, along with an effective penetration depth /spl lambda//spl tilde//sub J//spl prop//spl radic/(1/j/spl tilde//sub c/) which is larger than /spl lambda//sub J//spl prop//spl radic/(1/j/sub c/). The role of these effective parameters is demonstrated by fitting the peaks in I/sub c/(H) for junctions with both the width and length significantly larger than /spl lambda//spl tilde//sub J/ values, and by a re-scaling of field step structure found in current-voltage curves for commensurate fields which demonstrates their equivalence to the well-known zero field steps found in the absence of applied field.         Microwave surface resistance measurements of air-atomised spray deposited Tl-Ba-Ca-Cu-O thick films    A.P. Jenkins, L.Y. Su, K.S. Kale, M.J. Goringe, J.W. Burgoyne, D. Dew-Hughes and C.R.M. Grovenor Summary: The surface resistance (R/sub s/) of spray pyrolysed Tl/sub 2/Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thick films on 1 inch diameter finely polished yttria-stabilised zirconia disks has been measured using a TE/sub 011/ mode end-wall-replacement cavity at 20 GHz and 77 K. R/sub s/ values of 5.3 m/spl Omega/ and 1.3 m/spl Omega/ at 20 GHz and 10 GHz (scaled assuming an f/sup 2/ dependence) respectively were obtained. These results are the best recorded R/sub s/ values to date for thick films of any superconductor at the same frequencies and at 77 K. Transport critical current density (J/sub c/) measurements on the films exhibited values of >3/spl times/10/sup 4/ A/cm/sup 2/ at 77 K.         Ultra-high-field magnets for future hadron colliders    P.M. McIntyre, Weijun Shen and R.M. Scanlan Summary: Several new concepts in magnetic design and coil fabrication are being incorporated into designs for ultra-high field collider magnets: a 16 Tesla block-foil dual dipole, also using Nb/sub 3/Sn cable, featuring simple pancake coil construction and face-loaded prestress geometry; a 330 T/m block-coil quadrupole; and a /spl sim/20 Tesla pipe-geometry dual dipole, using A15 or BSCCO tape. Field design and fabrication issues are discussed for each magnet.         Recent developments in superconducting corrector magnet fabrication and measurements    R. Barrik, W. Czapla, R. Meinke, W. Robinson, C. Sylvester, A. Wernersbach, D. Wilson, B. Yager and Yuping Zhao Summary: Significant effort was devoted to the development and testing of corrector coils destined for use on the Superconducting Super Collider (SSC). Several process technologies used in the manufacture of correction coils were evaluated, including the "direct wire" process. Fabrication of corrector coils using the direct wire process involves the precision placement of superconducting wire coated with adhesive using a numerically controlled five-axis mill. This process is capable of supporting the fabrication of several magnet types and shapes. Improvements in the direct wire process resulted in the construction of three corrector coils configured as dipole magnets that exhibited excellent performance characteristics during power testing. A high bandwidth data acquisition system capable of correlating signals from a quench antenna array with magnet voltage taps was developed to analyze the performance characteristics of these corrector magnets. This paper describes the fabrication techniques, the analysis system, and performance results of these superconducting corrector coils.         Non quadratic RF losses in niobium sputter coated accelerating structures    C. Durand, W. Weingarten, P. Bosland and J. Mayer Summary: Low field Q-values of more than 10/sup 10/ and maximum accelerating gradients E/sub a/ between 10 and 15 MV/m have been obtained in superconducting mono-cell and multi-cell accelerating cavities between 350 and 1500 MHz. The superconductor is niobium, which is magnetron-sputtered as a thin film (/spl sim/1-2 /spl mu/m) on a cavity made from copper sheet. The dependence of the slope of Q vs. E/sub a/ on temperature and frequency can be explained by RF magnetic flux trapped within intrinsic defects.         Author Index (1994 - Part 1)    No author information available Summary: Not available

© Copyright 2009 All Rights Reserved. Developed for IEEE Applied Superconductivity Conference by InControl Productions, Inc..